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Bilateral energy conference

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Materials for electrochemical energy conversion - from modular to large-scale energy generation and storage

Electrochemical energy generation and storage is becoming an area of increasing interest, due to factors related to the increased penetration of renewable energy, limitations related to intermittency of renewable energy, limitations in other energy storage approaches, and the high theoretical efficiencies possible with most electrochemical devices. An emphasis has grown in the scale of deployment and both modular, dispersed solutions and large-scale approaches are being investigated. Many of the approaches are still highly dependent on materials advances as key enabling elements.

Scope:

Electrochemical energy conversion devices include batteries (primary and secondary), fuel cells, electrolyzers, and flow batteries. Historically, these devices have been primarily investigated for their use at relatively low energy or power levels with few examples that have approached the megawatt or megawatt-hour level. In order to make a greater impact on the electrical energy system the scale of these devices and their deployment needs to increase significantly. Traditional large scale electricity generating approaches, such as natural gas, coal and nuclear power plants have significant benefits (on a per KW basis) tending towards larger scales. Electrochemical devices typically have reduced gains in the economy of scale and make smaller distributed systems another interesting potential approach. Cost competitiveness remains a barrier for larger wide spread adoption of these technologies, and materials approaches are being pursued.

Electrochemical energy conversion devices have the ability to fit into larger energy systems in a number of ways. They can serve as sources of electricity generation from fuels (fuel cells), they can convert electrical energy in chemical form (electrolyzers), or they store electrical energy for some period of time and return electricity back at some later time (secondary batteries, flow batteries, reversible fuel cells).

In the area of energy generation, fuels (most notably natural gas) can be directly converted by fuel cells into electrical energy, often with useful heat (combined heat and power) as a valuable byproduct. Solid oxide fuel cells (SOFCs), molten carbonate fuel cells (MCFCs), phosphoric acid fuel cells (PAFCs) including those based on polybenzimidazole(PBI) and proton exchange membrane fuel cells (PEMFCs) have all been explored for their applicability in energy generation.

In the area of electrochemical conversion of electrical energy to fuel, specifically water electrolyzers, the scale of deployment to enable functions such as load leveling needs to be increased significantly. A number of new projects/programs are looking into the possibility of large scale electrolysis. The historic approach has been focused on aqueous potassium hydroxide as an electrolyte, although increasing interest in being given in the areas of solid oxide, proton exchange membrane, and alkaline membrane electrolysis. Each of these approaches has different limitations ranging from struggles with intermittent/high temperature operation to efficiency/precious metal catalysis to durability and lifetime.

In the area of electrical energy storage (secondary batteries, flow batteries, reversible fuel cells) the direct competition is with technologies such as pumped hydro and compressed air. These competing technologies don’t scale well down to small sizes and are limited geographically available. Depending on the specific technology the issues range from cost, durability, energy density and/or efficiency.

Contributions are sought in all areas where electrochemical energy devices are being investigated.

Topics to be covered by the symposium:

  • Polymer electrolyte fuel cells, including high temperature PBI/phos acid systems
  • Alkaline membrane fuel cells
  • Solid oxide fuel cells
  • Flow batteries
  • Electrolysis
  • Membranes, electrolytes, separators
  • Electrocatalysts
  • Electrodes
  • Cost
  • Performance
  • Durability

Symposium organizers:

 

Bryan S. Pivovar
National Renewable Energy Laboratory
15013 Denver West Parkway
Golden, CO 80401
USA
Phone: +1 303 275 3809
Fax: +1 303 275 3840
Bryan.pivovar@nrel.gov

Deborah Jones
Institut Charles Gerhardt de Montpellier UMR 5253
CNRS - Universite Montpellier II
Aggregates, Interfaces and Materials for Energy
Place Eugene Bataillon, Building 15, CC 1502
34095 Montpellier cedex 5
France
Phone : +33 467 14 3330
Fax : +33 467 14 3304
Deborah.Jones@univ-montp2.fr

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Solid Oxide : Gilles Taillades and Deborah Jones
09:00
Authors : M. Torrell, A. Meadowcroft, A. Morata, M. Burriel1, K. Kendall, M. Kendall, A. Tarancón.
Affiliations : M. Torrell, Catalonia Institute for Energy Research (IREC) Jardins de les Dones de Negre, 1, 08930-Sant Adrià del Besòs, Barcelona, Spain; A. Meadowcroft, Adelan, 10 Weekin Works, 112 Park Hill Road, Birmingham, B17 9HD, UK; A. Morata, Catalonia Institute for Energy Research (IREC) Jardins de les Dones de Negre, 1, 08930-Sant Adrià del Besòs, Barcelona, Spain; M. Burriel Catalonia Institute for Energy Research (IREC) Jardins de les Dones de Negre, 1, 08930-Sant Adrià del Besòs, Barcelona, Spain; K. Kendall Adelan, 10 Weekin Works, 112 Park Hill Road, Birmingham, B17 9HD, UK;M. Kendall Adelan, 10 Weekin Works, 112 Park Hill Road, Birmingham, B17 9HD, UK; A. Tarancón Adelan, 10 Weekin Works, 112 Park Hill Road, Birmingham, B17 9HD, UK;M. Kendall Adelan, 10 Weekin Works, 112 Park Hill Road, Birmingham, B17 9HD, UK;

Resume : This work analyses the electrochemical performance of 6 mm diameter Ni-YSZ/YSZ/SDC/LSCF anode supported microtubular solid oxide fuel cells (SOFC). The study was motivated by the good match with the portable system requirements and the microtubular SOFC cells properties. The studied cells show high thermal shock resistance, low degradation ratios, good electrochemical performance and excellent mechanical robustness. Results and methodology of dynamic and stability electrochemical measurements at intermediate temperatures (700ºC-750ºC) are discussed. Cells were measured under pure H2 as fuel and open air cathode. Microstructure evolution and mechanical problems has been evaluated by the authors and correlated with the cell working conditions. The performance of 20cm2 tubular cells show a maximum power density of 300 mW/cm2 and 4.5 kW of long term total power output at 7.5 A. A detailed post-test analysis of cells by SEM-EDX is of main value to understand the causes of failure and the cells microstructure evolution. Fuel utilization, current collection and electrode stability are described as key factors for a high performance and durability tests.

CC.CC.1.1
09:15
Authors : Joonho Park, Ikwhang Chang, Sanghoon Ji, Suk Won Cha
Affiliations : Seoul National University

Resume : In this study, we successfully fabricated thin film solid oxide fuel cells (TF SOFCs) supported by nanoporous substrates. We applied atomic layer deposition process in order to achieve defect-free membranes. It is verified that the TF SOFCs can be scaled up to millimetre scale of lateral dimension, even if they have only hundreds of nanometres thick membranes. Moreover, the open circuit voltage values were close to the theoretically expected values. This implies that the fuel cells were mechanically stabled in spite of the extremely high aspect ratio of the cross sectional geometry. We also investigated how the cathode morphology affects the ohmic and the faradaic resistances and how the sheet resistance works in the enlarged thin film fuel cells. Finally, we managed to develop an additional current-collecting structure on top of the cathode, which turned out to enhance the overall electrochemical performance of the fuel cells.

CC.CC.1.2
09:30
Authors : E. Xuriguera (1) (2) (3), M. Morales (1), A. Cirera (2), M. Segarra (1)
Affiliations : (1) IN2UB, Departament de Ciència dels Materials i Enginyeria Metal•lúrgica, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain; (2) MIND/IN2UB, Electronics Department, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain; (3) DIOPMA S.L., Baldiri i Reixac 1, 08028 Barcelona, Spain

Resume : Microtubular solid oxide fuel cells (MT-SOFCs) have received a great interest during last decade, as they present many advantages, such as a rapid start-up and shut-down operation, high thermal-shock resistance and high volumetric output power density. They possess multiple potential applications like power sources for portable devices. The improvement of electrode microstructures is crucial to achieve a high cell performance. Compared to the cathode coatings deposited by conventional techniques, three-dimensional nanofiber network cathodes present several advantages, such as a high porosity, high percolation, continuous pathway for charge transport, good thermal stability, and excellent scaffold for infiltration. In this work, nanofiber lanthanum strontium cobaltite with samaria-doped ceria (LSC-SDC) cathodes for MT-SOFCs were fabricated by the electrospinning method. Microtubular supports of NiO-SDC were shaped by gel-casting method. After spray-coating the electrolyte, the LSC-SDC cathode was deposited by electrospinning technique. Previously, suitable spinning suspensions based on PVA and PVP systems were prepared. The effects of the different processing parameters, such as solution viscosity, binder-solvent ratio, electrical parameters and sintering temperatures on the cathode microstructure were investigated in order to optimize the fiber and porous diameters and porosity. SEM observations showed a high microstructural porosity that can lead to a significantly improvement of the gas diffusion.

CC.CC.1.3
09:45
Authors : E.S. Kravchenko, L.V. Makhnach, V.V. Pankov
Affiliations : Belarusian State University, Chemistry Department

Resume : The new oxides with nominal compositions Sr4-y(Ti,Mo)xNi2-xO7+δ were obtained. Examination by XRD showed a close similarity with the reference pattern of Sr3Ti2O7 with the Ruddlesden-Popper type of structure. Full profile Rietveld refinement in space group 14/mmm confirmed this structure type. During the refinement procedure, the lattice parameters, positional and displacement parameters of atoms were refined. The Ni, Ti and Mo species are assumed to occupy the octahedral positions of Ti ions in the Sr3Ti2O7 structure in accordance with the initial nominal compositions. Refinements of the site occupancies showed that oxygen vacancies are located mainly in O1 sites. Examination of the high-temperature XRD patterns collected in situ in the temperature range 30-850°C showed no visible structural changes for the compositions investigated. However, changes of slopes in the temperature behaviour of the cell dimensions and considerable increase of the thermal expansion coefficients were observed between 500 and 600°C. At that changes of lattice expansion and thermal expansion coefficient are much more pronounced in c-direction, which is associated with the possible change of the oxygen stoichiometry during the heating of the powder. This observation favors our finding that oxygen vacancies are located mainly in the O1 sites in apical octahedral positions, sharing two layers of the [Ni/TiO6] octahedra.

CC.CC.1.4
10:00 Break    
10:30
Authors : Gilles Taillades
Affiliations : ICGM-AIME Université Montpellier 2

Resume : Among all types of fuel cells, the solid oxide fuel cell (SOFC) remains very attractive with respect to its high-energy efficiency, modularity and excellent fuel flexibility. However high operating temperatures in conventional SOFCs (800-1000 °C) cause problems in terms of both long-term durability and cost of materials. In this context, Proton Ceramic Fuel Cells (PCFCs) have received great interest in the last few years. This presentation is focussed on recent developments in electrolyte, anode and cathode materials for PCFC and will overview the state of the art and results obtained in our laboratory in the framework of the FP7 METPROCELL project. The advances made recently in terms of stability and power performance show potential for the development of the next generation of Solid Oxide Fuel Cells based on proton-conducting electrolytes.

CC.CC.1.5
11:00
Authors : E. A. Kotomin, R. Merkle, Yu. A. Mastrikov, M.M. Kuklja, J. Maier
Affiliations : Max Planck Institute for Solid State Research, Heisenbergstr., Stuttgart, Germany; Institute for Solid State Physics, University of Latvia, Riga, Latvia, Materials Science and Engineering Dept., University of Maryland, College Park, USA

Resume : In this talk, we discuss calculated from first principles the atomic and electronic structure of oxygen vacancies, their formation and migration energies in the bulk and in the surface layer, the defect-induced electronic density redistribution, and dependence of defect properties on the chemical composition of the (Ba,Sr)(Co,Fe)O3 (BSCF) (Fe/Co ratio). Our calculations confirm that the O-vacancy formation and, in particular, migration energies in BSCF are considerably smaller than in similar (La,Sr)MnO3 (LSM) and (La,Sr)(Co,Fe)O3 (LSCF) perovskites which explains its good performance. The gradual increase of these energies with an increase of the iron content is explained by analysis of the calculated density of the states. We discuss also briefly the problem of complex perovskites stability with respect to the decomposition into mixture of cubic and hexagonal phases or parent perovskites and oxides. Based on the calculated formation and migration energies of oxygen vacancies and adsorbed oxygen atoms at the LSM surface, we calculated the rates of elementary steps in ORR and suggested different scenatios of this process in LSM, BSCF, LSCF as a function surface coverage with adsorbed atoms and oxygen vacancy concentration. We predict that in both LSCF and BSCF perovskites the dissociation of surface peroxide or superoxide ion occurs with assistance of Vo, their encounter being the rate- determining step. M. Kuklja, E. Kotomin, R. Merkle et al, PCCP 15, 5443 (2013).

CC.CC.1.6
11:15
Authors : J.G. Grolig, J.-E. Svensson, J. Froitzheim
Affiliations : Environmental Inorganic Chemistry, Chalmers University of Technology Kemivägen 10 SE-41296 Göteborg

Resume : In order to reach high power densities in solid oxide fuel cells, planar fuel cell elements are usually stacked together by metallic interconnects. To reach low costs and good performance steels are the material of choice. Metallic interconnects face three major material challenges; degradation due to oxidation, evaporation of chromium which poisons the cathode and the degradation of the electrical conductivity because of the growing oxide scale. For a sufficient performance regarding these three issues, protective coatings have to be applied – this leads to additional costs. For cost savings cheaper base materials such as AISI 441 coated with intelligent protective coatings seem to be promising. Additionally both steel as well as the coating process need to be feasible for mass production. We investigated AISI 441 industrially coated with a high performance double layer coating of 10 nm cerium (inner layer) and 640 nm cobalt. The performance of chromium evaporation, corrosion rate and electrical degradation was monitored. The electrical properties could be linked to the evolving microstructure during the different stages of exposure. Both the durability of the electric performance and the oxygen uptake (mass gain) followed a similar trend. Chromium evaporation could be decreased by 90 % compared to the uncoated substrate material.

CC.CC.1.7
11:30
Authors : V. Sadykov1,2, N. Mezentseva1,2, Yu. Fedorova1, A. Lukashevich1, E. Smal1,2, M. Simonov1, M. Arapova2, A. Zadesenets3, O. Smorygo4 , A.-C. Roger5, K. Parkhomenko5
Affiliations : 1Boreskov Institute of catalysis, Novosibirsk, Russia; 2Novosibirsk State University, Novosibirsk, Russia; 3Nikolayev Institute of Inorganic Chemistry, Novosibirsk, Russia; 4Institute of Powder Metallurgy, Minsk, Belarus; 5University of Strasbourg, Strasbourg, France

Resume : Nanocomposites based upon complex oxides of rare-earth and transition metal cations with perovskite, fluorite, spinel, pyrochlore structure (possess high oxygen mobility and reactivity) and supported Ni, Co, Ni+Ru, Co+Ru nanoparticles were prepared using optimized sophisticated procedures. Catalysts were characterized by combination of diffraction, spectroscopic and kinetic methods and tested in reactions of steam/oxysteam reforming of methane, biogas, ethanol, acetone, glycerol (both as powders and layers on heat-conducting structured substrates) in lab/pilot-scale reactors. Efficient activation of H2O on reduced sites of oxide support, fuels-on Me particles and fast oxygen diffusion to Me/support interface provide fast transformation of fuels into syngas by red-ox route preventing coking. Strong metal-support interaction ensures sintering stability of metal alloy nanoparticles. Optimized catalysts provide a high yield of hydrogen (H2 content up to 50%) in steam reforming of biofuels in IT range. O2 addition to the feed suppresses coking providing stable performance. Power density up to 0.85 W/cm2 at 800 oC was obtained in the IR mode (H2O/CH4=2) for planar SOFC with thin YSZ layer on Ni/YSZ substrate using catalyst plate attached to anode. Support by Russian Fund of Basic Research Project RFBR-CNRS 12-03-93115, Integration Project 8 of SB RAS-NAN Belarus, FP7 Projects OCMOL and BIOGO is gratefully acknowledged

CC.CC.1.9
11:45 Lunch    
 
High Temperature PEM/ Flow Batteries : Thomas Steenberg and Peter Fischer
14:00
Authors : A: Hans Aage Hjuler, Hector Garcia, Thomas Steenberg B: Qingfeng Li, Jens Oluf Jensen, Lars N. Cleemann
Affiliations : A: Danish Power Systems, Bldg. 207, 2800 Lyngby, Denmark B: Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Lyngby, Denmark

Resume : High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) provide an attractive alternative to the Low Temperature (LT) PEM fuel cells in specific applications. Some of the advantages are fuel flexibility (e.g. hydrogen or reformate), efficient cooling, no need for humidification and higher value of excess heat. Polybenzimidazole (PBI) membranes doped with phosphoric acid have been demonstrated to be the most successful electrolyte system in order to achieve high temperature operation. Fuel cell systems based on this type of membranes have demonstrated the feasibility and potential of the technology. A number of ongoing projects in Denmark and internationally aim at the demonstration of the technology for various applications. Among these applications are HT-PEMFC for combined heat and power (CHP) purposes, as APU’s and range extenders. A number of challenges have been recognized to improve the performance, including slow kinetics of oxygen reduction at the cathode, strong adsorption of acidic anions on catalysts, platinum utilization and resistance losses. Addressing these issues is of fundamental and technological importance for the commercialization of HT-PEMFCs. Our recent efforts are focused on optimization of single cell performance will be described. In this communication we update the progress we have achieved in the last few years. Those are related with the optimization of the individual manufacturing processes. Establishment of consistent procedures for the PBI polymer synthesis, catalyst preparation and final MEA configuration are critical steps in order to achieve low batch to batch variations. Further efforts are made to quantify and reduce losses within the MEAs of HT-PEMFCs. Ohmic losses related to the membrane electrolytes and electrodes have been determined by electrochemical impedance spectra and polarization measurements. The Pt utilisation at the cathode is investigated and correlated to the overpotentials of MEAs. Recent progress within MEA development has resulted in a performance of more than 700 mV of cell voltage at a current density of 200 mA/cm2. An operating point of 500 mV at 500 mA/cm2 has been demonstrated. Long term durability at a constant current density of 200 mA/cm2 has been achieved of more than 10.000 hours with a strong indication to reach 20.000 hours. A correlation between variables and degradation modes are needed to fully understand degradation mechanism towards achieving longer durability. Finally perspectives and future development of the HT-PEMFC technology will be outlined. Acknowledgements The authors thank the Danish programs EUDP and Energinet.dk for financial support.

CC.CC.2.1
14:30
Authors : Fosca Conti (1,2), Jürgen Wackerl (1), Pierre Dams (1) and Carsten Korte (1)
Affiliations : (1) Institute of Energy and Climate Research (IEK-3), Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany (2) Department of Chemical Sciences, University of Padova, I-35131 Padova, Italy

Resume : High temperature polymer electrolyte fuel cells (HT-PEFC) typically work at 120-200°C and are mainly based on phosphoric acid (PA) swollen basic polymer membranes like polybenzimidazole (PBI). Although PA doped PBI membranes were investigated in several experimental studies, the kinetic of the adsorption process, the molecular interactions between the PA molecules and the polymer chains, polycondensation equilibria of the PA molecules as well as the implications on the proton conductivity is not finally illuminated. In this work, we have investigated the adsorption process of PA on m-PBI and a commercial AB-PBI derivative (Fumapem AM-55). A number of membranes (cross and uncross-linked) has been prepared at different doping level and analysed to elucidate the adsorption process of the PA as function of temperature, acid concentration and chemical equilibria between PA derivatives. Impedance measurements, Karl Fischer titration method and RAMAN spectra have been used to characterise the membranes. The thermodynamic aspects related to the adsorption process have been analysed with different kinetic models. Considering own and literature data on non-crosslinked m-PBI, a BET-like adsorption kinetics explains the behaviour of this polymer type satisfactorily. Using the RAMAN data, different regions in the BET-like isotherm can be correlated to the protonation of the polymer chain, formation of H-bonds directly to the chain and indirectly to still adsorbed PA molecules.

CC.CC.2.2
14:45
Authors : Christoph Heinzl1, Tanja Ossiander1, Markus Perchthaler2, Stephan Gleich1, Katharina Hengge1, Christina Scheu1
Affiliations : 1 Department of Chemistry, Ludwig-Maximilians-University Munich, Butenandtstr. 11, 81377 Munich, Germany; 2 Institute of Chemical Engineering and Environmental Technology, Graz University of Technology, Steyrergasse 21, 8010 Graz, Austria

Resume : Over the last several years high-temperature polymer electrolyte membrane fuel cells (HT PEMFCs) have gained substantial interest in research. They operate above 100°C and therefore benefit from faster reaction kinetics on the electrodes, increased catalytic activity and simplified heat management. One of the many remaining challenges of HT-PEMFCs is their limited lifetime. By incorporating inorganic nanoparticles (NP) in a polybenzimidazole (PBI) -based matrix several membrane properties and the overall lifetime of the fuel cell could be improved considerably. We synthesized silica NP from tetraethoxy silane (TEOS) by an in-situ sol gel procedure and cross-linked them to the PBI polymer chains with a linker [1]. The size, shape and distribution of the silica NP as a function of the used TEOS content were investigated by transmission electron microscopy (TEM). Besides the investigation of the influence of the NP on the thermal, chemical and mechanical properties, long-term fuel cell operation tests were performed. By doing so, an optimal content of silica NP could be defined. Further investigation focused on the degradation effects occurring at the fuel cell electrodes. By applying TEM based techniques we found that the catalyst NP agglomerate and that the morphology of the electrode changes. [1] T. Ossiander, C. Heinzl, S. Gleich, F. Schönberger, P. Völk, M. Welsch, C. Scheu, J. Membr. Sci. 2014, 454, 12-19.

CC.CC.2.3
15:00
Authors : Fischer, Peter; Caglar, Burak; Frank Wandschneider; Gerber, Tobias
Affiliations : Fraunhofer Institute for Chemical Technology ICT

Resume : A redox flow batteries can be regarded as a hybrid between a battery and a fuel cell. In a plain consideration, a flow battery can be regarded as a rechargeable fuel cell. In fact, fuel cell techniques can be adapted successfully to the needs of redox flow batteries. But usually these adaptions uses quite different approaches to cope with the corrosiveness and the special needs of the battery chemistry. In this talk, a broad overview of different research activities at Fraunhofer ICT in the field of flow batteries will be given, and parallels to fuel cell research will be drawn. The research activities cover basic battery chemistry, materials as well as the battery stack and system. Typical adaptions, which were developed at Fraunhofer ICT are highly conductive corrosion resistant bipolar plate materials, battery models of cell and stack, test devices for material testing as well as analytical tools like segmented cells. Later were developed at Fraunhofer ICT in collaboration with the fuel cell group at German Aerospace Centre (DLR). These research activities are all connected with the installation of a big battery storage installation at Fraunhofer ICT. A 20MW/20MWh all Vanadium redox flow battery storage (VRFB) will be installed in combination with a 2 MW wind turbine. The installation will start next year with the erection of the battery research building.

CC.CC.2.4
15:30
Authors : B. Huskinson1, M.P. Marshak1&2, C. Suh2, S. Er2, M.R. Gerhardt1, C.J. Galvin2, X. Chen2, A. Aspuru-Guzik2, R.G. Gordon1&2 and M.J. Aziz1
Affiliations : 1) Harvard School of Engineering and Applied Sciences, 29 Oxford Street, Cambridge, MA, 02138 USA; 2) Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge MA, 02138 USA

Resume : Wide-scale utilization of flow batteries is limited by the abundance and cost of the energy storage materials. We have developed a flow battery based on the aqueous redox chemistry of small organic molecules called quinones. The redox active materials contain no metals and can be very inexpensive. The molecules undergo fast and reversible two-electron two-proton reduction to hydroquinones on carbon without the addition of electrocatalyst. We will report the performance of an aqueous flow battery involving the quinone/hydroquinone couple.[1] At the time this abstract is being written, the peak galvanic power density exceeds 0.6 W/cm2 at 1.3 A/cm2. The round-trip electric-to-electric efficiency is 80% at 0.125 W/cm2. The galvanic voltage efficiency is 87% at 0.25 A/cm2. After 100 deep charge-discharge cycles, the capacity retention is 99.986% per cycle. The absence of active metal components in both redox chemistry and catalysis represents a significant shift away from modern batteries. This new approach may enable massive electrical energy storage at greatly reduced cost. [1] B. Huskinson, M.P. Marshak, C. Suh, S. Er, M.R. Gerhardt, C.J. Galvin, X. Chen, A. Aspuru-Guzik, R.G. Gordon and M.J. Aziz, “A metal-free organic-inorganic aqueous flow battery”, Nature 505, 195 (2014).

CC.CC.2.5
15:45
Authors : Thomas A. Zawodzinski, Jr , Che-Nan Sun, Zhijiang Tang, Douglas S. Aaron, Jamie Lawton, Amanda Jones, Emma Hollmann, Alexander B. Papandrew and Matthew Mench
Affiliations : Chemical and Biomolecular Engineering University of Tennessee. Knoxville, TN 37996; Physical Chemistry of Materials Group Oak Ridge National Laboratory, Oak Ridge, TN 37831; Mechanical, Aerospcae and Biomedical Engineering University of Tennessee. Knoxville, TN 37996

Resume : The development of high performance redox flow battery (RFB) cells requires the improvement of component performance. Unfortunately, much of the detailed scientific and technological understanding needed to achieve that performance was lacking as we began our efforts. At the outset of our team’s work on RFBs, we quickly realized that a number of kinetic, resistive and mass transfer losses and species cross-over through the membrane were unsatisfactorily high. Accordingly, we set out to systematically improve the cell internal resistances to improve the technology. This led us to change the typical cell design and material sets used. At the same time, we began to collect extensive data on the underlying properties of the materials to guide further improvements in material properties. To illustrate this approach, we describe in some detail our efforts on Vanadium Redox Flow Batteries. In this presentation, we will describe our path to achieve significant performance enhancement at the technological level. This includes the development of diagnostics that helped to refine our understanding of kinetic and mass transport phenomena in the cells. We will describe the introduction of and results from a variety of electrochemical and other methods to rigorously characterize these processes. The overall process has led to a demonstration of an increase of roughly 20 times the peak power achievable in the cell. We are now cycling cells at ~ ten times the typical commercial rate with higher unidirectional efficiency. Compared to research on other batteries or on fuel cells, very little detailed and careful work on membranes for RFBs has been presented. Several aspects of transport and related phenomena in these membranes are more complex than for other cases. Nonetheless, a systematic evaluation framework is needed. Such a framework consists of several types of information: (i) composition of the membrane system, i.e. uptake of counter- and co-ions and solvent as a function of composition of external bathing solution; (ii) description of species transport coefficients, including diffusion coefficients for ions and solvent and coupling coefficients describing the effects of interactions amongst species. These are supplemented by various thermodynamic analyses to provide insights into factors controlling the transport. In addition, it is useful to have simple descriptions of the primary observables in the operating cell, such as the changes in composition as a function of operation of the cell. We have started to systematically obtain this information for several battery types. Uptake by Nafion and related PFSA membranes has been determined by combinations of gravimetric and titration measurements for membranes exposed to sulfuric acid (vanadium flow battery), HCl and HBr. These have been coupled to conductivity measurements. In Figure 1, we show typical results for uptake of sulfuric acid by the membranes, plotted in several different ways to reveal various aspects of the uptake phenomena. In Figure 2, we show conductivity results. These illustrate general trends observed for all acids thus tested. Acid uptake increases with increasing bathing acid concentration, while water uptake decreases. Conductivity first slightly rises and then plummets with increasing bathing acid concentration. The decrease in conductivity arises from two separate phenomena, dehydration of the membrane and, surprisingly, acid uptake into the membrane. Uptake of vanadium into this system further decreases the membrane conductivity. For diffusion measurements, we have focused to date on monitoring the transport of a single species at a time through the membrane. In Figure 3, we show some raw data obtained using EPR to detect cross-over of vanadium ions. The experiment consisted of monitoring vanadium arriving across a membrane of a separated cell through which a test solution of V(IV) in sulfuric acid was circulated. We are exploring several variants of this experiment to enable each species to be probed since not all vanadium ions are EPR-active. One interesting phenomenon that we have observed in such experiments is the coupling of the flux of protons and vanadium, leading to unexpected effects of concentration on diffusion experiments. We are now developing an irreversible thermodynamic framework to analyze such experiments.

CC.CC.2.6
16:15 Break    
 
Poster Session : Bryan Pivovar and Deborah Jones
16:30
Authors : Doohun Kim, Yoon-Cheol Ha, Chuhyun Cho, Won-jae Lee, Chil-Hoon Doh
Affiliations : Battery Research Center, Korea Electrotechnology Research Institute, Chagwon, Republic of Korea

Resume : A novel technique of electrical explosion has been used for nanomaterial synthesis by a single-step process. However, it was known that in principle the electrical explosion of Si is not possible due to the fact that applying a high voltage on Si wire having relatively high electrical resistance leads to a current flow through surface plasma formed along the wire which disables the resistive heating of Si. In this presentation, we will show the successful application of electrical explosion to silicon nanoparticle synthesis and the electrochemical properties of Si/C nanocomposites derived from the nanoparticles. The electrical explosion of Si was successfully applied using a liquid media to suppress the unfavorable surface plasma generation. The physical and chemical properties of the produced materials were analyzed by XRD, FE-SEM, HR-TEM and the performances of the Si/C composites as an anode for Li ion batteries were investigated by electrochemical charge/discharge measurements. The Si/C composites obtained under the explosion in hexane and ethanol consist of a core-shell structure with a compact graphitic carbon on the Si particle surface which cause detrimental effects against Li ion diffusion. However, we found that Si explosion in methanol minimized the formation of the carbon phase on the surface of nano-sized Si. The Si/C nanocomposite after a simple pyrolysis with carbon precursor showed a high capacity with an excellent cycle performance.

CC.CC/P3..1
16:30
Authors : Umer Farooq1, 2, Adnan Yaqub1, 2, Syed Atif Pervez1, 2, Jeong-Hee Choi1, Kim Doohun1, Chil-Hoon Doh1, 2
Affiliations : 1-Korea Electrotechnology Research Institute 2-Department of Electrical Functionality Materials Engineering

Resume : Lithium-ion batteries are considered to be the best available energy storage technology in today’s electronics, upcoming EVs and high energy storage grid stations. These commercially used Li-ion batteries have graphite as negative electrode material but it offers limited theoretical capacity of 372mAh/g. Therefore some alternative anode materials are required to replace traditional graphite. In recent years, an impressive research has been conducted to introduce the Silicon (Si) as anode material in lithium ion batteries on commercial level. Many factors like electrolyte, binder, electrode composition ratio etc play a key role in electrochemical performance of an electrode [1]. In this work, we conducted a comprehensive study to examine the electrochemical performance of Si based anode material with a novel Cu-SPB conductive material. Nanosized Si/Graphite composite was synthesized in first step by using solid state method. Afterwards, this nanosized Si/Grpahite powder was tested for battery application with Cu-SPB. We examined structural dimensions of electrode composite using field emission electron microscopy (FESEM) and elemental mapping using energy dispersive x-ray spectroscopy (EDS). Phase analysis was carried out using x-ray diffraction (XRD). Introduction of Cu-SPB showed improvement in all electrochemical parameters and this improvement is attributed to high conductive nature of Cu.[2] In conclusion, the electrochemical performance of an electrode highly depends on selection of conductive material in electrode. Cu-SPB exhibited remarkable improvement with Si as anode active material in terms of all electrochemical properties like specific discharge capacity, columbic efficiency and stable capacity retention.

CC.CC/P3..2
16:30
Authors : Baikov Yu.M.
Affiliations : Ioffe Physical Technical Instutute of RAS

Resume : Solid protonic conductors based on crystalline hydrates of alkaline metals are studied from 2007. Our attention was directed to solid compositions of KOHnH2O (0,5 n 2). Melting points are 100°C (n=0.5), 146°C (n=1), 42°C(n=2). These particular points of phase diagram KOH – H2O are interesting first of all for basic research, but intermediate ‘n’ have to be studied from applied viewpoint owing to composite formation at low temperatures and high proton conductivity more 1 mS/cm. However to use these compounds on electrochemical devices traditional electrode material –graphite – and of any type it is necessary to find electrode materials compatible with solid hydroxide compounds. Metallic Pd, Ti, TiFe and Sn are already presented together with traditional electrode material –graphite. As Carbon and Tin are the members of IV group of periodical table we are starting to study the classical semiconductors Si. The preliminary data have showed that the electrochemical activity sufficiently depend on a type of charge carrier and a total conductivity. Taking into account our opportunity we have decided to use p-Ge to to continue our pioneering searches. Besides it may be note that using Germanium and Carbon allows to consider the opportunity: i) to combine with Solar Cells, ii) to use as low-drain power sources in microelectronics.

CC.CC/P3..3
16:30
Authors : Jong-Won Lee, Beom-Kyeong Park, Nurhadi S. Waluyo, Seung-Bok Lee, Tak-Hyoung Lim, Seok-Joo Park, Rak-Hyun Song
Affiliations : New and Renewable Energy Research Division, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon, 305-343, Republic of Korea

Resume : Solid oxide fuel cells (SOFCs) offer several advantages over low-temperature fuel cells, e.g., high thermodynamic efficiency, fast electrode kinetics, and direct use of hydrocarbon fuels. An interconnect provides electrical connection between adjacent cells and separates fuel and oxidant gases. The interconnects can be divided broadly into two categories – ceramic and metallic interconnects. A thin and gastight ceramic layer is deposited onto a porous support, and metallic interconnects are coated with conductive ceramics to improve their surface stability. Here, we report on SOFC interconnect coatings based on perovskite-type oxides. A dual-layer ceramic interconnect is first discussed that consists of an n-type conducting (Sr,La)TiO3 layer on the anode side and a p-type conducting (La,Sr)FeO3 layer on the cathode side. Then, protective perovskite coatings of (La,Sr)MO3 (M = transition metals) on metallic interconnects are presented, which are capable of mitigating oxide scale growth and inhibiting Cr evaporation. The synthesis of perovskite oxides and their electrical/thermal expansion properties are discussed in detail, followed by a description of coating processes. We demonstrate that the dense interconnect or protective layers are fabricated by a simple and cost-effective coating–sintering process and they exhibit low resistance and high stability under SOFC operating conditions.

CC.CC/P3..4
16:30
Authors : Jong Deok Park, Sung Ho Lee, and Haekyoung Kim
Affiliations : School of Materials Science and Engineering, Yeungnam University, Gyeungsan, South Korea

Resume : With the expanding need for large electrical energy storage systems in connection with renewable energy sources, flow batteries, have been enormously considered due to their high flexibility in upgrade and low cost associated with scale-up. Of all the flow batteries, vanadium redox flow battery (VRFB) use of same element in both half-cell solutions that overcomes the inherent issue of cross contamination by diffusion of different ions across the membrane. Together with the absence of any toxic emissions, the vanadium redox flow battery has demonstrated its uniqueness in terms of safety and long life cycle. Typical charge–discharge reactions of a VRFB involve two vanadium redox couples, V(II)/V(III) and V(IV)/V(V), in the negative and positive half-cells, respectively. In a fashion similar to most batteries, electrons are transferred between the two electrodes through the external circuit during the charge and discharge processes. In a VRFB, the ion exchange membrane is a key component as an ionic conductor and separator: it not only provides an ionic conduction pathway between the two electrolytes but also prevents mixing of the negative and positive electrolytes. The crossover of ions through the membrane, with the diffusion of vanadium ions from one half-cell to the other due to the concentration gradients between the two electrolytes, will result in self-discharge and thus the loss of the chemical energy. In this study, the hybrid membrane of inorganic materials with perfluorinated organic membrane were fabricated and characterized in terms of ionic conductivity and permeability. The ionic conductivity was measured with four point probe method and the permeability was measured with UV spectroscopy. The hybrid membrane exhibited similar ionic conductivity with perfluorinated organic membrane and 30% lower permeability than perfluorinated organic membrane.

CC.CC/P3..5
16:30
Authors : Hyunuk Kim, Young-Ju Lee, Sung-Jin Lee, Yong-Sik Chung2, Yoonjong Yoo*
Affiliations : Korea Institute of Energy Research;2Chonbuk National University

Resume : Carbon papers (CPs) were fabricated using wet-laying carbon fibers (CFs) and polyacrylonitrile (PAN) fibers. Scanning electron microscopy revealed that the PAN fibers tightly interconnected the CF junctions with the pores. The tensile strength of the carbon webs (CWs) increased as the fraction of PAN fibers used as the binder increased. The CW fabricated with 0.15 wt.% PAN fibers had a tensile strength six times greater than that of a bare CW. Moreover, by mixing the CFs with PAN fibers in water, the CFs separated from each other in the webs due to the interruption of hydrophobicity between the CFs. After the CWs were pyrolyzed at 1200 C in the presence of a phenolic resin, the PAN fibers maintained their morphology due to their high carbon content. The resistance of the CPs with high PAN fiber content was significantly lower than that of a bare CP due to the interconnection of the CFs by the carbonized PAN fibers.

CC.CC/P3..6
16:30
Authors : Arbi Fattoum, Mourad Arous
Affiliations : Research Unit: Materials Environment and Energy, chemistry department, faculty of sciences 2112 Gafsa, Tunisia; Laboratory of Composite Materials, Ceramics and Polymers, physics department, faculty of sciences 3038 Sfax, Tunisia.

Resume : In this work we investigated composite electrolytes of 25 and 50 mol% cross linked polyvinyl alcohol by oxalic and citric acids for fuel cell application. We studied the effects of crosslinking on thermal, structural, conductivity and dielectric relaxations. The glass transition temperature is increased indicating the decrease of the local mobility of the polymer chains. X-ray diffraction showed the decrease of the cristallinity degree. The Ac conductivity studied between 10-1Hz and 1MHz showed a power law response in the high frequency range. This behavior characterizes the charge transport in disordered materials. At low frequencies the Ac conductivity is governed by the electrode/sample interface polarization. The dc conductivity is thermally activated and the activation energy is deduced from an Arrhenius fitting. The use of the dielectric permittivity indicates the presence of a relaxation process attributed to electrode/sample interface polarization and another relaxation process attributed to alpha relaxation of the polyvinyl alcohol matrix.

CC.CC/P3..7
16:30
Authors : Abdelkrim KAHOUL
Affiliations : Université F. Abbas de Sétif, Faculté de Technologie, 19000- Sétif, Algérie

Resume : It is well known that the electrochemical activity in perovskite oxides are frequently related to electrical resistivity and electronic delocalisation. From this point of view, the semi-conducting double perovskite seems to be a good candidates to show interesting electrocatalytic properties for oxygen reduction and evolution reactions. With this purpose in mind, we present the results concerning La doping effects on the structural (Fig.1), grain morphology, and electrical properties of Sr2-xLaxFeMoO6 oxides. We investigate also the electrochemical behavior of such compounds prepared as oxygen electrode films in energy conversion device.

CC.CC/P3..8
16:30
Authors : Zhong-Kuan Luo,Fang Wang,Li Zhou,Yan Pang, Yang-Hai Xu,Jing Chen,Dong Liu
Affiliations : College of Chemistry and Chemical Engineering,Shenzhen University

Resume : Lithium-air battery, with a theoretical specific energy of 11000 Wh kg-1, which is very close to that of gasoline and far exceeds that of current state-of-art lithium-ion battery, has aroused worldwide interest and would be a most promising candidate for grid storage and to flourish the electric vehicle market. Low discharge rates and poor cycle life are the main limiting issues that hinder its commercialization and practical use. Here, a Li+ modified CNT cathode and perfluorinated compound containing LiTFSI/sulfolane electrolyte has been employed in lithium-air batteries, successfully realizing better reversible formation/decomposition of lithium peroxide (Li2O2) at the cathode upon cycling. With a specific capacity of 1000 mAh g−1 and at a current density of 0.10 mA cm−2, a superior cycling performance over 180 circles can be delivered. Even at a higher discharge rate of 0.50 mA cm−2, 252 stable cycles can be obtained in the voltage scope of 2.0V to 5.0V. Such great promotion can be attributed to a synergy between the novel Li+ modified CNTs cathode and inimitable perfluorinated compound containing LiTFSI/sulfolane electrolyte. The former, containing Li+ and possessing a homogenous and well-ventilated structure, not only speeds the Li+ transport and reaction kinetics, but also provides a number of active sites and large product accommodation space for electrochemical reaction. The later, as an oxygen carrier, can significantly improve the solubility of oxygen in the electrolyte, thus enhancing the diffusion coefficient of oxygen in the electrolyte to promote the high discharge rate capability.

CC.CC/P3..9
16:30
Authors : Ying-San Chui, Wenjun Zhang
Affiliations : Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, PR China

Resume : Graphite is currently the most widely used lithium-ion battery (LIB) anode material. However, the theoretical capacity of graphite is only 372 m Ah/g, which is unsatisfactory for high energy and power density LIBs in the future. Recently, MoS2 has attracted particular research interest due to its analogous layered structure to graphite with much higher theoretical capacity of 670 m Ah/g. In this work, monodispersed MoS2 nanospheres were successfully synthesized via one-step hydrothermal reaction in the presence of polyvinylpyrrolidone (PVP). The process is facile and scalable. The size of the MoS2 nanospheres decreased with increasing the PVP concentration. The MoS2 nanospheres (80nm in diameter) delivered a large reversible capacity of 840 m Ah/g and exhibited good cycling stability (98.37% capacity retention after 50 cycles) under current density of 0.5C, while the Coulombic efficiency remained over 99.5%. In particular, the MoS2 nanospheres demonstrated high rate capability with 675 mAh/g at 5C and 554 m Ah/g at 10C. By comparison, the MoS2 nanospheres showed enhanced electrochemical performance over conventional MoS2 nanosheets in terms of cycling stability and rate capability. The improved performance can be attributed to the extensive surface area provided by the MoS2 nanospheres for Li-MoS2 interactions, as well as shorter Li-ion diffusion pathway within the MoS2 nanospheres.

CC.CC/P3..10
16:30
Authors : Sergei Vassel, Natalia Vassel
Affiliations : Rostov branch of MSU TM

Resume : There are two well known ways of generating energy, using salt and fresh water mixing. First of them is mechanical way, when a vessels with a salt and fresh water are separated by a semi-permeable membrane. The disadvantage of this way is high energy loss during electricity generation, because electric power generates in two stages. The second one uses ion selective membranes. In this case electric power generates in one stage. The disadvantage of second way is a high resistance of ion-selective membranes. We develop the third way of converting entropy of fresh and salt water mixing into electrical energy, using concentration galvanic cell. Of course NaCl solution is not the best working solution for concentration galvanic cell. We may use Ag/AgCl electrode, but they are too expensive for high-scale generation. So we have such a scheme of our cell: salt water || semi-permeable membrane || working solution of high concentration-working solution of low concentration || semi-permeable membrane || fresh water. In this case NaCl solution never takes part at the reaction, but absorbs water from working solution of high concentration. We try several working solutions, such as salts of Ag or Cu. The most interesting results we got using sulfuric acid as working solution and Pb/PbSO4 electrodes. In contrast to the traditional concentration galvanic cells, where the potential difference depends of the lg c1/c2, in sulfuric acid solution we have practical linear dependence of the electrode potential on the concentration of sulfuric acid. We have this effect because galvanic cell uses not only entropy factor, but also the energy of exothermic reaction of sulfuric acid dissolving in the water.

CC.CC/P3..11
16:30
Authors : Sergei Vassel, Natalia Vassel
Affiliations : Rostov branch of MSU TU

Resume : We develop a concept, calculate an efficiency and made a model of new devise for converting heat energy into electricity. The work of our devise is based on the reaction H2SO4 nH2O=H2SO4*nH2O Q. This reaction is reversible over a high temperature range. Direct reaction can be used for electricity generation and reverse reaction can be performed in temperature gradient. The work of suggested devise consists of two stages: distillation of sulfuric acid solution in temperature gradient and generating electrical energy in galvanic cell. Calculation shows, that the efficiency of this way of heat converting to electricity could be 4,5% if T1=313 K (40 C) and T2=293 K (20C). Increasing T1 up to 373K we can increase the efficiency of the devise up to 12-15%. The model of this devise is consist of two blocks: distillation block and block of concentration cells. Distillation block has a standard for such devises construction. Block of concentration cells consist of two lead batteries with different concentrations of electrolyte.

CC.CC/P3..12
16:30
Authors : Veerapandian Ponnuchamy ; Stefano Mossa ; Valentina Vetere
Affiliations : INAC/SPrAM/GT ; INAC/SPrAM/GT ; CEA / DRT/DEHT/LCPEM, CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble, France.

Resume : The electrolyte plays an important role in Lithium ion batteries(LIB's). Organic solvents such as cyclic and linear carbonates are commonly used in LIB's. It is very important to investigate the structure and dynamics of Li+ ion in pure and mixed solvent compositions. Although there are some DFT studies of Li+ ion with single solvent, in several applications mixtures of three solvent are used to improve stability and transport properties. Here we focus on three carbonates such as cyclic ethylene carbonate(EC), propylene carbonate(PC) and linear dimethyl carbonate(DMC). The DFT method provides a detailed account for the electronic structures of carbonates and Li+ ion including clusters Li+(S)n (S=EC,PC,DMC n=1-4) and mixed cluster Li+(EClDMCmPCn) (l+m+n=4) in gas phase as well as in solvent environment and including the effect of PF6- anion. The results show that carbonates mainly interact through the intermolecular Li+ --O=C. We have studied the coordination shell around Li+ for three solvents. We have investigated the Mulliken charges and vibrational modes with solvent molecules varying from 1 to 4 and thermodynamics properties used to clarify the stability of clusters.Study of clusters of EC and PC reveals that PC tends to substitute EC in the solvation shell. These DFT calculations were performed at the level of GGA/PBE using TZP basis. This study will be used to develop Molecular Dynamics studies that will help to understand the transport properties of Li+ ion in LIB's.

CC.CC/P3..13
16:30
Authors : Dharmesh Kothari, D. K. Kanchan, Poonam Sharma
Affiliations : Department of Physics, Faculty of Science, The M. S. University of Baroda, Vadodara 390 002, Gujarat, India

Resume : In the present study, Lithium based Li1.3 Al 0.3-x Yx Ti1.7 (PO4)3 (LAYTP) system ceramic electrode material has been prepared using solid state method. Different concentrations of Y2O3 have been used to study the effect on conductivity. The conductivity studies are carried out using impedance spectroscopic analysis and the variation in crystallinity is investigated using XRD technique. The results indicate decline in the ionic conductivity as a result of doping of Yttrium a rare earth element but into superior type of electrode. The resulting material formed has a better grain boundary conductivity at microstructure level. Further studies are solicited using other trivalent cations like Ga3+ and Sc3+ in place of Y3+ in the above system.

CC.CC/P3..14
16:30
Authors : Yu-Shu Lin(1), I-Chun Chang(1), Ting-Ting Chen1, Po-Chin Chen(2), Hsin-Tien Chiu(2), Chi-Young Lee(1)*
Affiliations : 1. Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu 30013,Taiwan, ROC 2 .Department of Applied Chemistry, National Chiao-Tung University, Hsinchu 30010,Taiwan, ROC

Resume : In this work, nanostructural tin oxide is synthesized by hydrothermal approach using SnCl2 as precursor and polyvinylpyrrolidone (PVP) as an exfoliating and carbonated agent in alkali solution in various time periods. SnO microsheets and Sn3O4 nanosheets with thickness in the range of 50~60 nm can be acquired at 24 hours. The aggregation of pure phase Sn3O4 nanosheets was obtained while the reaction time is prolonged to 30 hours. The anode of lithium ion battery made by as synthesized Sn3O4 nanosheets was examined at discharge- charge rate (0.3C) by using EC/EMC/ DMC ( volume ratio=1:1:1) as electrolyte. The reversible discharge capacity is 228 mAhg-1 after 30 cycles. Intercalating and integument PVP occupy the active sites in Sn3O4 nanosheets obstructing the lithiation process, which leads to poor discharge capacity. In order to improve the battery performance, anodes made by PVP removed Sn3O4 nanosheets and self carbonized Sn3O4 nanosheets by PVP pyrolysis under argon atmosphere were further examined.

CC.CC/P3..15
16:30
Authors : L. Popovici, A.M.I. Trefilov, S.-M. Iordache, A.-M. Iordache, A. Balan, I. Stamatin*
Affiliations : University of Bucharest, Faculty of Physics, 3NanoSAE Research Centre, 405 Atomistilor Str., P.O. Box 38, Bucharest-Magurele, Ilfov, Romania, 077125 *Corresponding author: istarom@3nanosae.org

Resume : The consumption of fossil fuels and the need for clean energy has lead to the fast development of renewable energies and especially of fuel cells. The classical configuration, 2D membrane electrode assembly (MEA) has permitted the development of fuel cells stacks, with increased voltage and current density up to 1000 mA/cm2 respective, with specific weight ~4 g/W. To improve performances and simultaneous with reducing of specific weight and cost need new approaches in Fuel cells design. In this respect the study deal with a new geometry of PEMFC developed on cylindrical carbon xerogel synthesized using a proprietary technology. Cylindrical PEMFC could be considered an improved alternative to the classical configuration. At the standard Pt loading for anode and cathode (0.3 mg Pt/cm2, respectively 0.6 mg Pt/cm2) and Nafion membrane the PEMFC reach similar performances at lower specific weight around of 1-2 g/W. Keywords: PEMFC, xerogel, catalyst, centrifugal

CC.CC/P3..16
16:30
Authors : Adriana Balan (1), Alexandra Trefilov(1), Catalin Luculescu(2), Stefan Iordache(1), Ioan Stamatin(1)
Affiliations : (1)University of Bucharest, Faculty of Physics, 3Nano-SAE Research Centre, P.O.Box MG-38, 077125 Magurele, Romania (2) National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, RO-77125, MG-36, Magurele-Ilfov, Romania

Resume : The aim of this study is to design a hybrid electrolyte with a three-layer structure: a proton conducting polymer layer on one side of a resorcinol-formaldehyde (RF) porous structure, while the other is impregnated with an anion conducting polymer. The sandwich structure enables protons generated at the anode to progress toward the center and meet hydroxyl ions created at the cathode to form water, which is directed through the porous RF network. The hybrid electrolyte ensures an efficient water management by preventing water presence at electrode sites and, hence, related problems: corrosion, low fuel efficiency. Specific structural features are identified by means of Fourier transform infrared spectroscopy, while information on the polymer/porous RF network interfaces are revealed by scanning electron microscopy. Electrochemical characteristics are studied through electrochemical impedance spectroscopy. Further on, the hybrid electrolyte is tested in H2/air fuel cell system, with a Pt catalyst load of 1mg/cm^2 at both anode and cathode, reaching a maximum current density of 400-600mA/cm^2 at a voltage of 0.6-0.7V.

CC.CC/P3..17
16:30
Authors : Catalin Ceaus(1), Adriana Balan(1), A.M. Iordache(1), *Ioan Stamatin(1), Catalin Luculescu(2)
Affiliations : (1)University of Bucharest, Faculty of Physics, 3Nano-SAE Research Centre PO Box MG-38, Bucharest-Magurele, Romania (2)National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, RO-77125, MG-36, Magurele-Ilfov, Romania *corresponding author: istarom@3nanosae.org

Resume : Looking for high quality graphene and their mass production, today are devised a series of experimental methods from basics (e.g. scotch tape method, kish graphite, high pyrolitic graphite) to graphene oxide reduction with different reducing agents (hydrazine, tetraborohydrides). Few studies deal with graphite exfoliation at moderate pressures and temperature (close to 4000C) in different solvents (e.g. water, ethanol, tetrahydofuran, DMF, methanol). On the other hand, the expandable graphite (intumescent graphite) is a stack of intercalated graphene with different inercalants like nitric, sulphuric, acetic compounds. The graphene result from a high oxidative process of intercalation such as nitric-sulphuric acids followed by flash heating at high temperatures (up to 4000C) to insert sulphate compounds (sometimes referred to as graphite bisulphate). Based on these considerations, this study deals with graphite exfoliation in few layers (up to five layers) graphene using reactive species developed by water and ethanol in different mixtures under critical–supercritical conditions, at a set temperature and time. Structural investigation by atomic force microscopy, Raman spectroscopy and scanning electron microscopy reveal structures with a single to a few layers (up to five) of graphene. Cyclic voltammetry, performed in a three electrode cell, in acidic and basic media, shows few reversible peaks in the range 750mV - 570mV (in 0.1M HClO4)... This report provides a simple and low-cost approach for the production of pure graphene sheets, with a wide range of applications: fuel cells, supercapacitors, solar cells, electrochemical sensors.

CC.CC/P3..18
16:30
Authors : A. Cucu, E. C. Serban, A. Balan, C.Ceaus, A-M Ducu, L. Popovici, I. Stamatin
Affiliations : University of Bucharest, Faculty of Physics, 3Nano-SAE Research Centre, MG-38, Bucharest-Magurele, Romania

Resume : Major drawbacks in fuel cells performance is determined by the oxygen reduction reaction (ORR) which is sluggish than the hydrogen oxidation reaction (HOR). Extensive researches made over the past decades have focused in improving the ORR kinetics by using different catalysts: noble metals (Pt), alloys, carbon materials, quinone, transition metals chalcogenides, transition metals carbides and heteropolyacids. One approach is to utilize heteropolyacids (HPA) as potential cathode mediators, due to their acidic and redox properties, their potential to carry complex counter-cations (e.g. H+, H3O+, H5O2+) and their thermal stability. Three types of heteropolyacids: phosphomolibdic acid, phosphotungstic acid and tungstosilicic acid where studied as redox mediators in the cathodic chamber. The experimental set-up consists of a bicameral fuel cell with Nafion membrane. The anodic chamber acts as the source of hydrated protons at a given potential (equivalent with a reversible hydrogen electrode); the cathode chamber contains the aqueous HPA mediators recirculate in different conditions of flow and oxygen concentration. Electrochemical impedance spectroscopy, cyclic voltammetry and polarization curves were carried out to identify kinetics mechanisms related to ORR improvement.

CC.CC/P3..19
16:30
Authors : Fleur Thissandier, Dorian Gaboriau, David Aradilla, Nicolas Berton, Nicolas Pauc, Thierry Brousse, Gerard Bidan, Pascal Gentile, Said Sadki
Affiliations : Fleur Thissandier ; Dorian Gaboriau ; David Aradilla ; Nicolas Berton ; Said Sadki : CEA Grenoble LEMOH/SPrAM/UMR 5819 (CEA,CNRS, UJF)/INAC 17 rue des Martyrs, 38054-Grenoble, FRANCE Fleur Thissandier ; Dorian Gaboriau ; Nicolas Pauc ; Pascal Gentile : CEA Grenoble/INAC SiNaPS Lab.-SP2M, UMR-E CEA/UJF 17 rue des Martyrs, 38054-Grenoble, FRANCE Thierry Brousse : Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP32229, 44322 Nantes Cedex 3, France Gerard Bidan : INAC/Dir, CEA/INAC Grenoble 17 rue des Martyrs, 38054-Grenoble, FRANCE

Resume : Double layer electrochemical supercapacitors are subjects of a growing attention, since they fill the gap between dielectric capacitors and batteries in terms of energy and power densities. Recently, supercapacitors based on nanostructured silicon were designed and showed promising performances. In particular, their compatibility with existing microelectronics processes and their ability to sustain millions of cycles at fast charging/discharging rates are of great interest for integrated power-source in Si-based microelectronic devices (MEMS, active RFID, sensors…). Highly doped, dense and hyperbranched silicon nanotrees (SiNTrs) have been grown by Chemical Vapor Deposition (CVD) via gold catalysis. Using different gold deposition methods or growth parameters, various morphologies have been studied. Electrochemical characterization of the electrodes and symmetric micro-supercapacitor were conducted in different electrolytes (NEt4BF4 (1M), PC and EMI-TFSI (1M), PC). We have demonstrated that the nanostructuration of silicon electrode with SiNTrs enhanced the supercapacitor capacitance (up to 900 µF.cm-2). Ionic Liquid based electrolyte (EMI-TFSI (1M), PC) also increased energy and maximum power densities (respectively up to 262 µJ.cm-2 and 225 mW.cm-2) with a remarkable stability to the charge/discharge cycling (less than 18% after more than one million cycles). F. Thissandier et al. Electrochem. Comm. 25, 2012 109–111 111 P. Gentile et al. Nanotechnology 2008, 19, 125608

CC.CC/P3..20
16:30
Authors : Jin-Hoon Yang1, Byung-Kook Kim2, Yeong-Cheol Kim1
Affiliations : 1School of Energy, Materials and Chemical Engineering, KoreaTech, Korea; 2High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Korea

Resume : Accepter-doped barium zirconate shows excellent bulk proton conductivity and chemical stability, while it shows poor proton conductivity at grain boundaries. Space charge layer model has been proposed to explain the poor proton conductivity at grain boundaries. The space charge layer at grain boundaries can be originated from positive-charge buildup due to the segregation of proton at the grain boundary. The proton segregation energy has been extracted by calculating the energy of a grain boundary structure with a proton at the grain boundary via density functional calculation. We found that the segregation energy varies with the proton concentration at the grain boundary and therefore considered its effect on the space charge layer model. To better explain the experimental conductivity data, a hybrid model including the structural disorder at the grain boundary was proposed.

CC.CC/P3..21
16:30
Authors : Yue Ma
Affiliations : Uppsala Univ

Resume : We designed and fabricated a bicontinuous carbon foam/Fe-doped SnO2 composite with hierarchical porosity as the high performance free-standing anode electrode for lithium ion batteries. The synthetic method involved the scalable nanocasting process of Fe-doped SnO2 using the high internal phase emulsion polymer (polyHIPE) as the structural support as well as the carbon source. The as-developed C/Fe-doped SnO2 electrode is highlighted by several innovative design concepts: firstly, macroporous carbon foam derived from the pyrolysis of polyHIPE serves as the structural support for conformal SnO2 coating; secondly, the SnO2/C bicontinuous network not only provides facile electronic transport and electrolyte percolation, but remove the necessary usage of binder, carbon additive and massy metal current collector; thirdly, the deliberated choice of iron dopant (higher lithiation/de-lithiation potential versus LixSn) is designed to provide the dual functionalities of electrically wiring the Li-Sn system as well as the catalytic effect for re-oxidation of Sn. The electrochemical measurements were therefore conducted to demonstrate the high specific capacity of ~ 800 mA h g-1 up to 100 cycles, the high reversibility (~ 80% during the first cycle), excellent rate capability up to 4 A g-1, which presents the best cycling performance among tin-based free-standing electrodes in the open literature. Finally, the catalytic effect of Fe dopant on the reversibility of SnO2 was investigated through the in-situ characterization techniques and Mössbauer spectroscopy.

CC.CC/P3..22
16:30
Authors : C. Gutsche, M. Knipper, H. Borchert, T. Plaggenborg, J. Parisi
Affiliations : Department of Physics, Energy and Semiconductor Research Laboratory, University of Oldenburg, Oldenburg, Germany

Resume : In Vanadium redox flow batteries two Vanadium (V) electrolyte tanks with a V(2 /3 ) and a V(4 /5 ) electrolyte are used for energy storage. For charge and discharge the electrolytes are pumped through a reaction unit consisting mainly of two electrodes and a Proton Exchange Membrane (PEM) that separates both electrolytes. Here the V ions are reduced and oxidized. A promising approach for doubling the energy density of this system is the Vanadium air redox flow battery, in which the V(4 /5 ) electrolyte is replaced by water and Oxygen. The reactions are V(2 ) --> V(3 ) e(-) and O2 4H( ) 4e(-) --> 2 H2O for the discharge and vice versa for the charge. For the Oxygen Reduction Reaction (ORR) during discharge and the Oxygen Evolution Reaction (OER) during charge, catalysts like e.g. Platinum (Pt) are needed. V contamination of the water/air side of the reaction unit occurs because of the permeability of the PEM for V ions. Deposition of V compounds on the catalysts of the water/air side can reduce the system's efficiency. The aim of this work is to study via Electrochemical Quartz Crystal Microbalance (EQCM) measurements, under which conditions deposition of V compounds takes place on Platinum (Pt) nanoparticles. This method allows simultaneous electrochemical measurements at the working electrode on an oscillating quartz and the observation of material deposition via changes of the quartz? resonance frequency. Measurements of Pt nanoparticles and bulk Pt are compared.

CC.CC/P3..23
16:30
Authors : E. C. Serban, A. Balan, A. M. I. Trefilov, A. Cucu and I. Stamatin
Affiliations : University of Bucharest, Physics Department, 3Nano-SAE Research Centre, Atomistilor Street, Nr. 405, P.O Box 38, Bucharest-Magurele, 07712, Romania,

Resume : Urea Fuel Cells employ a non-toxic, non-flammable and transport-friendly (without pressurization need) fuel that can be easily recovered from waste water. The present study investigates the urea fuel cells performance, using a new membrane-electrode assembly based on an anion exchange resin in a polyvinyl alcohol polymer matrix. Composite membrane intrinsic properties are studied in terms of ion-exchange capacity (IEC), water content, transport number, and thermal stability. Results show an IEC and water content increase with resin content, while polymer glass transition temperature and melting points shift due to hydrogen bonding between polymer and resin. Urea fuel cell testing is performed using Pt/C at both anode and cathode, for different urea concentrations, ranging from 1 to 7 M.

CC.CC/P3..24
16:30
Authors : M. Sgambetterra 1, S. Brutti 2, V. Allodi 3, G. Mariotto 3, S. Panero 1 , M.A. Navarra 1
Affiliations : 1 Dipartimento di Chimica, Sapienza Università di Roma, P.le Aldo Moro 5, I-00185, Roma; 2 Dipartimento di Scienze, Università degli Studi della Basilicata, Via dell’Ateneo Lucano 10, I-85100, Potenza; 3 Dipartimento di Informatica – Università di Verona, Strada le Grazie 15, I-37134, Verona

Resume : Polymer electrolyte membrane fuel cells based on Nafion® electrolytes working at high-temperature and low-relative humidity (RH) are highly desirable since the need of noble metal catalyst is lower, poisoning effect of CO and sulphite is drastically reduced and the water management is simpler than for fuel cells working fully humidified at temperature below 80° C. The major issue of Nafion® membranes is the sharp decay of the conductivity responding to a decrease of its hydration. A promising strategy in order to improve performances under the above mentioned condition is the addition of an inorganic solid acid that helps in holding back water increasing meanwhile the number of acid site. Here a study about Nafion composite membranes, containing nanosized sulfated titania nanoparticles synthesized through an optimized 1-step synthesis procedure is reported. Peculiar membrane properties, such as ionic exchange capacity and water uptake ability will be described. A detailed thermal analysis investigation, as well as proton conductivity and hydrogen fuel cell performances will be also presented and discussed. Interestingly, despite minor proton conductivity under 100% RH, composite membranes of selected composition showed higher fuel cell performances under lower humidification, exhibiting a significant improvement, with respect to bare Nafion-based systems, of the maximum power and current density delivered under 30% RH and 70° C.

CC.CC/P3..25
16:30
Authors : V. Allodi1, S. Brutti2, M. Giarola1, M.Sgambetterra3, M.A. Navarra3, S. Panero3 and G.Mariotto1
Affiliations : 1 Dipartimento di Informatica – Università di Verona, Strada le Grazie 15, I-37134, Verona; 2 Dipartimento di Scienze, Università degli Studi della Basilicata, Via dell’Ateneo Lucano 10, I-85100, Potenza; 3 Dipartimento di Chimica, Sapienza Università di Roma, P.le Aldo Moro 5, I-00185, Roma.

Resume : Polymer electrolyte fuel cells based on Nafion membranes are able to work in a relatively low temperature range (70–100°C) but require operating relative humidity (RH) close to 100% in order to allow effective proton conduction. In order to develop proton-exchange membranes with adequate performances at low RH an attractive strategy consists of the incorporation of inorganic acidic materials into the host Nafion polymer. Sulfated metal oxides are actually attracting much interest as fuel cell membrane additives. This work concerns the characterization of both the nanosized TiO2 powders with high acidic properties to be adopted as fillers in Nafion-based polymer electrolytes and the obtained nanocomposite membranes. One step synthesis has been developed to obtain nanometer-sized sulfated titania particles. The sulfated TiO2 nanoparticles have been incorporated, in a range of amounts, in Nafion polymer membranes trough a solvent-casting procedure. Structural, morphological and vibrational properties of the sulphated titanium oxide particles and of the nanocomposite membranes have been investigated by several techniques including XRD, TEM, AFM, Raman and IR spectroscopies, and the results of this integrated characterization are here presented.

CC.CC/P3..26
16:30
Authors : O. Marconot (a), D.Buttard (a)(b), N. Pauc (a), A. Morin (c)
Affiliations : (a): INAC, CEA-Grenoble, 17 Avenue des Martyrs, Grenoble, 38054, France (b) : IUT-1, Université de Grenoble, 17 Quai Claude Bernard, Grenoble, 38000, France (c) : LITEN, CEA-Grenoble17 Avenue des Martyrs, Grenoble, 38054, France

Resume : Development of proton exchange membrane fuel cells (PEMFC) is limited by high cost of platinum catalyst. Nanostructuration of the cathode of fuel cells permits to enhance the mass and area activity of catalyst in oxygen reduction reaction and then to reduce the quantity of Pt used. Our goal is to elaborate very low cost carbon free cathodes with a high efficiency using only electrochemistry process in order to make vertically and highly ordered dense array of platinum nanotubes. First, a nanoporous anodic aluminum oxide (AAO) template is made on a silicon substrate. Then, pores are filled with copper by pulsed electrodeposition route. AAO is removed and we obtain highly ordered copper nanowires on silicon substrate. Platinum is deposited by galvanic displacement or electrodeposition on copper nanowires. Finally, the copper cores are etched giving only platinum nanotubes on the silicon substrate. We propose a crystallography study of copper nanowires and platinum nanotubes, first tests in fuel cells are realized (influence of geometric parameters sush as diameter, period and height will be discussed).

CC.CC/P3..27
16:30
Authors : Surya Subianto1, Sara Cavaliere1, Deborah Jones1, Jacques Rozière1, Sarah Burton2, John Blake2, Graham Hards2, Luca Merlo3
Affiliations : 1. ICGM, Aggregates, Interfaces and Materials for Energy, CNRS, Montpellier, France. 2. Johnson Matthey Fuel Cells Ltd., Sonning Common, UK 3. Solvay Speciality Polymers Italy S.p.A., Bollate, Milan, Italy.

Resume : Novel membranes have been designed for increased durability comprising low equivalent weight short-side-chain Aquivion PFSA modified by cross-linking and reinforcement. Cast membranes of 30 micron thickness have been extensively characterised for their proton conductivity and water uptake, and screened using in situ fuel cell protocols designed to specifically accelerate either mechanical or chemical degradation. A stack testing protocol was developed to simulate the usage that would be seen during an annual seasonal cycle for a micro-CHP application; with the winter cycle being a continuous high current density hold, the autumn and spring cycles including high and low current density holds, and the summer cycle including sequences of highly stressing on – off cycling. Between each of these seasonal holds a number of diagnostics were completed including polarisation curve analysis and hydrogen crossover testing. Stack testing for over 1,000 hours of the 4-cycle protocol clearly identified enhanced performance due to the decreased ionomer equivalent weight and increased durability compared to state-of-the-art non-reinforced membranes.

CC.CC/P3..28
16:30
Authors : J.R. Torres-Hernández1, A. G. Flota Robledo2, G. Pérez-Hernández1, J. Pantoja-Enríquez2, E. Ramírez-Morales1, D. Martínez-Hernández1, M. González-Solano1, E. Del Angel-Meraz1, M. Acosta-Alejandro1, C. Ricardez-Jiménez1
Affiliations : 1Universidad Juárez Autónoma de Tabasco, Avenida Universidad S/N, Zona de la Cultura, Col. Magisterial, Villahermosa, Centro, Tabasco 86040, México, 2Centro de Investigación y Desarrollo Tecnológico en Energías Renovables, UNICACH, Libramiento Norte No 1150, Tuxtla Gutiérrez, Chiapas 29039, México.

Resume : In this work we are presenting the results of structural and optical investigations of ZnO and Cu doped ZnO films using XRD, XDS, UV-VIS transmittance spectroscopy, and the application of these films in photocatalysis is demonstrated. Cu doped ZnO films were prepared by sol-gel method. The concentration of Cu utilized for doping ranged from 1% to 5 % by atomic weight. The average grain size for 5% Cu doped sample was in the range of 10-15 nm. The optical band gap was found to decrease with Cu concentration. The resistivity was found to decrease by one order after doping. The 5% Cu doped ZnO films showed an increased photocatalytic activity

CC.CC/P3..29
16:30
Authors : Dongwoo Kang, Hyeon Suk Shin
Affiliations : Two-Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology, UNIST-gil 50, Eonyang-eup, Ulju-gun, Ulsan 689-798 Republic of Korea. Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology, UNIST-gil 50, Eonyang-eup, Ulju-gun, Ulsan 689-798 Republic of Korea.

Resume : Chemically converted graphene, especially reduced graphene oxide (rGO), is considered as an important component for electrode material in energy storage devices such as supercapacitor and battery because of its high conductivity and high surface area. However, the two-dimensional (2D) sheets incline to restack during the electrode fabrication process, which lead to reducing the surface area and limiting the electron and ion transport. Here, we present a strategy to overcome stacking problems by changing the 2D graphene sheet into a three-dimensional (3D) sphere structure through capillary-driven assembly, followed by microwave-assisted thermal treatment. Adding a small amount of rGO to multi-wall carbon nanotube (MWNT) (e.g., 100:5 weight ratio) can synergistically transform the morphology and increase the specific surface area of its sphere structure. As-produced rGO/MWNT sphere undergo additional metal catalytic oxidation in air by silver (Ag) nanoparticles, resulting in holey carbon sphere with mesopores. Compared to flat and non-porous rGO sheets, the holey rGO/MWNT sphere can offer much higher specific surface area and better electrochemical performance in terms of specific capacitance.

CC.CC/P3..30
16:30
Authors : L. Pasquini(1,2), R. Narducci(1,2), P. Knauth(1), M. L. Di Vona(2)
Affiliations : (1) MADIREL, Aix Marseille Université (Campus Saint Jerome), 141 Traverse Charles Susini 13013 Marseille (2) Dip. Scienze e Tecnologie Chimiche, Univ. Roma Tor Vergata, Via della Ricerca Scientifica 00133 Roma luca.pasquini@etu.univ-amu.fr riccardo.narducci@uniroma2.it

Resume : The need to improve the distribution of resources on the earth, increasing the ease of energy and the need for reduction of pollution and the continuous increase of petrol cost has reinforced the interest in clean systems for energy conversion and storage for medium to large scale application. This has projected our attention to the study of polymeric membranes able to increase the efficiency of operation and decrease the costs of technologically advanced devices like redox - flow batteries and fuel cells. In our research, we studied different ionomer membranes for applications in fuel cells and redox-flow batteries and we focused our attention on the functionalization of aromatic polymers like PEEK, PSU and PPSU. For the realization of protonic conducting membranes we studied above all proton-conducting sulfonated aromatic polymers (SAP) stabilized via cross-linking SO2 bridges in presence of a reticulation agent (DMSO) . Furthermore, we synthesized and studied anion exchange membranes based on chlorosulfonated and chloromethylated aromatic polymers functionalized by secondary (like dimethylamine) or tertiary amines (like trimethylamine, 1,5-diazabicyclo-[4,3,0]-non-5-ene, 1,4-diazabicyclo[2.2.2]octane) with different basicity and different structure. The objective was to obtain membranes with high anionic conductivity, and excellent chemical and thermal stability. All the membranes were characterized by different techniques. TGA analysis gave us information about the decomposition and the stability of ionic exchange groups, while stability tests, water uptake, permeability and conductivity measurements, evidenced the behavior of the membranes in the working condition.

CC.CC/P3..31
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Acidic and Alkaline Polymer Electrolyte Fuel Cells : Tom Zawodzinski and Jacques Roziere
08:30
Authors : Ikwhang Chang1, Taehyun Park2, Jinhwan Lee3, Ha Beom Lee2, Sanghoon Ji1, Min Hwan Lee4, Seung Hwan Ko2, Suk Won Cha1,2
Affiliations : 1Graduate School of Convergence Science and Technology(GSCST), Seoul National University, Gwanakro 1 Gwanakgu, Seoul, 151744, Republic of Korea. 2Department of Mechanical and Aerospace Engineering, Seoul National University, Gwanakro 1 Gwanakgu, Seoul, 151744, Republic of Korea. 3Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701, Republic of Korea 4School of Engineering, University of California, Merced, 5200 North Lake, Merced, California 95343, USA.

Resume : Flexible polymer electrolyte fuel cells are made of novel current collectors including highly conductive metal nanowires with extremely high stretchability. Endplates with flexible current collectors maximize clamping forces under bent conditions, which is beneficial in reducing ohmic resistances. These cells show an increased power density as the radius of curvature of the cell decreases. Cells in an asymmetric configuration, where the thicknesses of plates at the anode and cathode sides are different, shows higher power density than symmetric cells because of enhanced normal pressure, and thus, decreased ohmic loss under a given cell curvature. The peak power density of a highly bent stack with a bending radius of 15.6 cm is measured to be actually larger than a flat stack by 95%.

CC.CC.4.1
08:45
Authors : Rameshwori Loukrakpam, Nina Hundertmark, Peter Strasser
Affiliations : Department of Chemistry, Chemical Engineering Division, Technical University Berlin, 10623 Berlin, Germany

Resume : Ethanol oxidation is known to have slow kinetics, sluggish adsorption and cleavage of C-C bonds and poisoning of the active sites on Pt catalysts by CO-intermediates. Complete ethanol electro-oxidation to CO2 involves 12 electrons per molecule, while partial oxidation leads to by-products like acetic acid or acetaldehyde, which reduce the faradaic efficiency of the anodic reaction of Direct Ethanol Fuel Cells. Efforts to develop highly active and selective electrocatalysts for ethanol oxidation reaction (EOR) have been concentrated on the addition of co-catalysts to platinum. The most promising family of EOR nanocatalysts are currently based on combination of Pt, Rh and Sn. Different electrocatalysts were prepared by simultaneous reduction or consecutive reduction of Pt, Rh and Sn precursor salts, using oleic acid and oleylamine as surfactants and tetradecandiol as the reducing agent in dioctylether. A uniquely comprehensive set of experimental techniques was employed to determine the composition, morphology and atomic-scale structural coherence of the synthesized ternary nanoalloy electrocatalysts, including inductively coupled plasma optical emission spectroscopy (ICP-OES), Cu Kα based and synchrotron-based X-ray diffraction (XRD), transmission electron microscopy (TEM) coupled with energy disperse X-ray spectroscopy (EDS), X-Ray photoelectron spectroscopy (XPS), etc. Cu Kα and synchrotron XRD studies coupled to atomic pair distribution function analysis showed that PtRhSn/C nanoalloy had PtSn-nigglite type structure with Rh occupying random Pt sites. Electrochemical experiments showed that the catalytic activity towards EOR of chemically homogeneous PtRhSn/C is the highest when compared to those of the other catalysts. Also, at higher temperature of 60 degrees Celsius (similar to low temperature fuel cell), a dramatically increase activity was seen, with faster kinetics making this catalysts potentially viable for intermediate temperature fuel cells. In situ FTIR data showing formation of CO2 during the EOR as a result of C-C bond splitting in ethanol at an early potential is also a very significant result which will help in further understanding the mechanistic aspects of these electrocatalysts towards EOR and has the potential to help in the future design of DEFC catalysts.

CC.CC.4.2
09:00
Authors : Micheal Burke, Brendan Kennedy,Mary Manning, Alan Blake, Aidan Quinn.
Affiliations : Tyndall National Institute

Resume : We describe a wafer-scale, clean-room fabrication process for nanoporous platinum electrodes using anodized aluminum oxide (AAO) nanopore arrays on silicon (with aspect ratios > 10) combined with ~20 nm coatings of platinum using thermal atomic layer deposition through alternating exposures to (Trimethyl)methylcyclopentadienylplatinum (IV) (MeCpPtMe3) and oxygen.The electrochemical performance of these nanoporous titanium nitride electrodes are characterised using electrochemical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Subsequently their suitability for applications in "on chip" energy storage is discussed.

CC.CC.4.3
09:15
Authors : Samuele Galbiati, Arnaud Morin, Nicolas Pauc
Affiliations : CEA Grenoble LITEN/LCPEM Lab (Galbiati, Morin) CEA Grenoble DSM/INAC SiNAPS Lab (Pauc)

Resume : In this work we present a new PEM fuel cell membrane-electrode architecture based on an array of self-standing Pt nanotubes (Pt-NTs). The Pt-NTs array is produced by electron beam evaporation of Pt on a porous Anodic Aluminum Oxide (AAO) layer. After the Pt deposition, the coated AAO layer is stuck onto a Nafion® membrane by hot pressing and alumina is chemically dissolved. As a result a membrane-electrode couple based on an array of Pt nanotubes is obtained. The developed production scheme is made of a few steps and is based on a simple deposition technique. Pt-NTs (length: 200 nm, Øint: 100-200 nm, twall: 10-20 nm) have stiff walls and parallel direction, the array density is around 109 NTs/cm2, its Pt loading is lower than 300 µg/cm2. The behavior of the nanotubes array has been tested ex-situ in half-cell setup (0,5 cm2 active area) by measuring cyclic voltammetry under dry N2, O2 and CO. Results have been compared with the ones measured on a conventional Pt/C dispersion electrode.  The active surface of the NTs array electrode is limited: 12 m2/gPt vs 50 m2/gPt of the Pt/C electrode  The whole surface of the NTs is electrochemically active vs 50% of the Pt/C electrode  The CO poisoning test indicates improved gas accessibility  The ORR surface activity is improved: 35 µA/cm2 vs 28 µA/cm2 of the Pt/C electrode  ORR mass activity is still low: 5 A/gPt vs 15 A/gPt of the Pt/C electrode In-situ fuel cell tests (17 cm2 active area) of this new electrode structure have been performed under both dry and humidified air and oxygen. The electrode shows very good levels of Pt surface exploitation and satisfactory water management features. These experiments represent a novelty in the field and demonstrate the sustainable application of this nanostructure in real systems.

CC.CC.4.4
09:30
Authors : Rameshwori Loukrakpam(1), Lin Gan(1), Chunhua Cui(1), Qiuyi Yuan(3), Marc Heggen(2), Stanko Brankovic(3), Valeri Petkov(4), Peter Strasser(1)
Affiliations : (1)The Electrochemical Energy, Catalysis and Materials Science Laboratory, Technical University Berlin, Berlin 10623, Germany (2)Ernst Ruska Center for Microscopy and Spectroscopy with Electrons, Forschungszentrum Juelich GmbH, 52425 Juelich, Germany (3)Department of Electrical and Computer Engineering, University of Houston, Houston, TX 77204, USA (4)Department of Physics, Central Michigan University, Mt. Pleasant, MI, USA

Resume : In recent years, innovative surface and subsurface alloy structures and morphologies, such as Pt skins, Pt monolayers, Pt core-shell particles, size and shape-controlled Pt particles, and Pt nanostructured thin films are being explored with activity enhancements approaching, or exceeding PEMFC commercialization targets. However, for viable PEMFCs, not only initial catalytic activity but also long-term durability is a requirement, which has remained as an unachieved goal. Extended Pt alloy electrocatalysts with unique surface morphology and electronic surface properties provided ideal models for understanding the improvement in reaction kinetics for the oxygen reduction reaction (ORR). In practical Pt alloy nanoparticle electrocatalysts, however, it is quite challenging to design materials to understand the ORR activity owing to the surface complexity and the leaching of transition metal during electrocatalysis. Here, we will first describe the design and synthesis of shaped Pt-Ni nanoparticles with controlled composition segregation and particle size; and study the structural and compositional behaviors during electrocatalysis. The composition, size and shape of the nanoparticles were controlled by simply changing the synthetic conditions. The surface composition of the Pt-Ni was measured using X-ray photoelectron spectroscopy (XPS), the bulk composition by energy dispersive X-ray spectroscopy (EDX) and inductively coupled plasma mass spectrometry (ICP-MS), and the element distribution was verified by aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy (STEM-EELS), respectively. The results demonstrated that for larger particle size ~9 nm the ORR activity mainly depended on the surface composition and Pt shell thickness. Specifically, we uncovered a unique intraparticle compositional segregation in pristine octahedral Pt-Ni nanoparticles, showing the Ni segregation at the facets and Pt segregation at the edges/corners. Such segregation led to drastic Ni dissolution from the facets and hence severe activity degradation. Our results provide important insights for designing new generation Pt fuel cell catalyst with both high activity and high stability. Effective utilization of the high energy density of ethanol as a fuel for polymer electrolyte fuel cells is contingency of complete oxidation of ethanol to carbon dioxide. Major problems associated with the development of electrocatalysts for ethanol oxidation are the high content of Pt and partial oxidation of ethanol to acetaldehyde and acetic acid instead of complete oxidation to carbon dioxide via the 12 electron process. Despite extensive work on ethanol oxidation catalysts, it is difficult to get C-C bond splitting without compromising on the Pt content. Our recent studies on Pt monolayer and sub-monolayer on Au/C nanoparticles will be discussed as a viable option for anodic reactions in DEFCs. Au/C@Pt(II) and Au/C@Pt(IV) were synthesized using a Cu mediated SLRR electrochemical method. Electrochemical testing of these electrocatalysts showed that Au/C@Pt(II) had substantially higher activity towards EOR than Au/C@Pt(IV). The effect of Pt cluster sizes on the Au surface and the tensile strain on Pt due to the underlying Au and their effect on EOR will be discussed. The mechanism of EOR on these electrocatalysts was also studied using in-situ FTIR to understand whether there is complete or partial oxidation of ethanol and CO2 production was clearly observed during the reaction confirming the involvement of 12 electrons. CO-adsorption in-situ FTIR studies to detect the change in the d-band energy will also be discussed.

CC.CC.4.5
10:00 Break    
10:30
Authors : Paul Paciok, Marcelo Carmo , Wiebke Maier, Juergen Mergel, Detlef Stolten
Affiliations : Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany and Chair for Fuel Cells, RWTH Aachen University, Germany

Resume : PEM water electrolysis represents a good alternative to store the excess of energy produced by intermittent power sources via hydrogen. However, conventional PEM electrolysers depend on scarce and expensive metals like Pt for the hydrogen evolution reaction (HER) and Ir for the oxygen evolution reaction (OER). One of the main tasks relies on the reduction of the noble metal amount while retaining or increasing the performance of the electrolyser. Thereby the influence of the decrease of the noble metal loading, and a possible degradation of the active material on the durability of the HER catalyst are both essential. In this study we investigate under electrolysis conditions, possible degradation issues like particle coarsening and particle detachment of a commercial Pt/C catalyst, using the identical location TEM method. For this purpose we simulate steady and dynamic operation modes of an electrolyser in a three electrode setup with a catalyst-coated TEM-Grid. In order to observe the effect of the electrolysis operation modes on the catalyst, identical locations on the TEM-Grid were examined before and after the experiments. Our study reveals that under the studied conditions, a migration of platinum particles occurs, resulting in the formation of large particle aggregates. The detachment of active material is also evident. Moreover, we demonstrate that IL–TEM reveals as a reliable ex situ characterization method to evaluate the stability of catalysts for PEM electrolysis.

CC.CC.4.6
10:45
Authors : Shaun Alia, KC Neyerlin, Arrelaine Dameron, Svitlana Pylypenko, Dave Diercks, Shyam Kocha, Bryan Pivovar
Affiliations : National Renewable Energy Lab; Colorado School of Mines

Resume : Extended, thin film electrocatalyst structures (ETFECs) have been of interest for fuel cell applications due to their high activity and good durability. Traditionally these catalysts have been limited to low electrochemically available surface areas (ECA). Our efforts have focused primarily on using galvanic displacement to create novel fuel cell catalysts. These efforts have resulted in high ECA, reaching values as high as 90 m2/g and mass activities as high as 2000 mA/mg Pt (at 900mV IR free). This mass activity is almost an order of magnitude greater than that of baseline Pt/C catalysts when characterized using rotating ring disc electrodes. These materials have remaining concerns regarding stability and the ability to effectively incorporate into high performance membrane electrode assemblies. We will discuss different materials developed to date in terms of synthesis and characterization. Additionally, efforts to synthesize related structures for electrolysis applicactions are underway and the results to date as well as potential benefit of these structures in electrolysis systems will also be presented.

CC.CC.4.7
11:00
Authors : Marta Zaton, Deborah Jones and Jacques Rozière
Affiliations : ICGM, Aggregates, Interfaces and Materials for Energy, CNRS, Montpellier, France.

Resume : We will report the development of a nanofiber-network material enriched with cerium oxide nanoparticles as radical trap at the membrane electrode interface. The mitigation properties of such modified MEAs were verified in in situ OCV hold test conditions at low relative humidity 50 % and high temperature 90 ºC, with the radical scavenger interlayer oriented preferentially to the anode or to the cathode side. Reference membranes with an additional nanofiber layer but no cerium component were also examined to ensure that observable effects are due to the presence of radical scavenger. The result of OCV hold testing under these conditions show that whereas MEAs integrating non-modified Nafion®-212, or Nafion®-212 modified by an interlayer of nanofibre PFSA (no cerium oxide) only, show a marked drop in OCV with time, and end of life at <200 hours, an MEA comprising a cerium oxide nanofiber interlayer at the anode side gave very stable open circuit voltage and a significantly longer lifetime. Post mortem analysis of the MEAs and analysis of eluent water by liquid chromatography were combined to better understand the overall degradation process occurring in cerium enriched and cerium free MEAs, including X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM) analyses.

CC.CC.4.8
11:15
Authors : Vijay Shankar Rangasamy 1*, Savitha Thayumanasundaram 1, Jin Won Seo 2, Jean-Pierre Locquet 1
Affiliations : 1. Department of Physics and Astronomy, KU Leuven, Bus 2414, Celestijnenlaan 200D, 3000 Leuven, Belgium; 2. Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44 - bus 2450, B-3001 Leuven, Belgium

Resume : We report the vibrational properties and the changes in the degree of crystallinity of poly(ether ether ketone) (PEEK) membranes by using Fourier transform infrared (FTIR) spectroscopy. The changes in the vibrational modes of the functional groups present in the polymer due to sulfonation and the incorporation of functionalized silica particles are discussed. From the infrared spectra, the incorporation of sulfonic acid group in the polymer chain as well as in the functionalized silica nanoparticles was confirmed. We have attempted a non-destructive method to calculate the crystallinity of polymers by measuring the variations in the peak area intensity of the characteristic out-of-plane vibrations of the aromatic rings in the PEEK polymer with respect to a crystallinity-insensitive reference peak. These values were correlated to the crystallinity values calculated by Differential Scanning Calorimetry (DSC). High degree of sulfonation (DS) values decreased the crystallinity of the polymer, indicating the crystalline-to-amorphous phase transition in the polymer, which explains the improved ionic conductivity at high DS values. Keywords: SPEEK, FTIR, sulfonation, silica, crystallinity, DSC

CC.CC.4.9
11:30
Authors : R. Narducci , L. Pasquini , P. Knauth , M. L. Di Vona
Affiliations : Università di Roma “Tor Vergata” & Universitè d’Aix-Marseille ; Università di Roma “Tor Vergata” & Universitè d’Aix-Marseille ; Universitè d’Aix-Marseille ; Università di Roma “Tor Vergata”

Resume : The developed synthesis of anion exchange membranes is based on inexpensive aromatic polymers, such as polysulfone (PSU) and polyetheretherketone (PEEK), which are easy to produce and recycle with relatively little environmental pollution problems, are stable in alkaline media, present a low gas permeability, and are soluble in organic solvents. We synthesized anionic aromatic polymers by the reaction of a chloromethylated precursor with different degrees of chloromethylation (DCM) using various amines, such as trimethylamine and cyclic amines (DABCO, DBN). The amines were chosen because they are strong bases, present high values of steric hindrance and the positive charge is delocalized through long-range interactions or resonance; these features can help to prevent the Sn2 elimination by OH- and the ylide formation. In order to stabilize the membranes, we cross-linked the aminated polymers via sulfone bridges by simple thermal treatments with a small percentage of chlorosulfonated PEEK. In the case of trimethylamine, the anionic conductivity increases with the degree of amination until IEC = 1.6 eq/kg. The cross-linked ionomer and the ionomer with DBN show the highest stability in alkaline conditions. The TGA analysis shows the loss of water below 100°C, loss of ammonium groups around 140°C and the decomposition of the main chain around 500°C. The perspectives of this work are: determine the optimal degree of amination to balance high conductivity and low swelling and find the precursor with the highest stability in alkaline medium.

CC.CC.4.10
11:45
Authors : Bryan Pivovar, Matt Sturgeon, Chai Engtrakul, Dan Ruddy, Hai Long, Clay Macomber
Affiliations : National Renewable Energy Lab, 15013 Denver West Parkway, Golden, CO, 80401, USA

Resume : Anion exchange membranes are being developed for a number of electrochemical applications including fuel cells, electrolyzers and flow batteries. Most of the effort has focused on fuel cell applications and the use of these materials in alkaline membrane fuel cells (AMFCs). Historically, these materials have been limited due to their stability in the presence of hydroxide. Our team has been leaders in the area of probing hydroxide stability of covalently tetherablecations. We have investigated multiple different cations including those based on ammonium, sulfonium, phosphonium and imidazolium. We have investigated the impact of different substitution patterns on stability and found dramatic differences through specific substitution. We have also focused on baseline stability measurements and protocols for testing the hydroxide stability of cations under high pH conditions. We will present a discussion on the current status of alkaline stable cations, and also present data for our membrane synthesis efforts that have focused on perfluoro anion exchange membranes.

CC.CC.4.11
12:00 Lunch    
 
Electrolysis : Jurgen Mergel and Bryan Pivovar
13:30
Authors : J. Mergel, M. Carmo, D. Fritz, D. Stolten
Affiliations : Forschungszentrum Jülich GmbH

Resume : Energy technology is currently undergoing a major transformation worldwide. The generally accepted factors driving this transition are climate change, supply security, industrial competitiveness and local emissions. However, hydrogen is envisaged as an important storage medium or energy carrier for transportation purposes in future energy systems where renewable energy sources are to play a major role in the energy mix. At the moment, commercial water electrolysis methods are only available in the areas of alkaline electrolysis and PEM electrolysis. This presentation describes the state of the art of the different electrolysis processes such as alkaline electrolysis, PEM electrolysis and high-temperature electrolysis. In addition, the challenges and the need for research and development for alkaline and PEM electrolysis will be identified so that water electrolysis can be realistically and sustainably applied in the mass markets after 2020 for hydrogen production using surplus electricity generated from renewable sources. Important challenges in the further development of alkaline water electrolysis include increasing the power density of stacks, enlarging the partial load range and reducing system size and complexity. PEM electrolysis development focuses on cutting costs by reducing the amount of noble metal catalysts required or substituting them with other materials without compromising performance values, as well as on improving long-term stability and increasing system size in the MW range.

CC.CC.5.1
14:00
Authors : Stefano Giancola1, Anita Skulimowska1, Alvaro Reyes-Carmona1, Marc Dupont1, Surya Subianto1, Sara Cavaliere1, Deborah Jones1, Jacques Rozière1, Eddy Moukheiber2 and Luca Merlo2
Affiliations : 1. ICGM, Aggregates, Interfaces and Materials for Energy, CNRS, Montpellier, France. 2. Solvay Speciality Polymers Italy S.p.A., Bollate, Milan, Italy.

Resume : Composite (organic-organic and inorganic-organic) membranes based upon the short-side-chain ionomer Aquivion® (of equivalent weights in the range 800-1000 g meq-1) have been developed for medium temperature proton exchange membrane water electrolysis. Membrane electrode assemblies were prepared using iridium oxide, synthesised via a hydrolysis method from the chloride precursor, as catalyst for the oxygen evolution reaction. It was deposited (2 mg cm-2) on the membrane either directly by spray deposition or by decal transfer. An extruded short-side-chain perfluorosulfonic acid Aquivion® membrane gives higher water electrolysis performance than a corresponding cast composite membrane with zirconium phosphate. However the lowest cell voltage was observed at 140 °C for an MEA prepared by decal transfer on to a nanofibre reinforced Aquivion® membrane, 1.55 V at 1 A cm-2. Membrane preparation and characterisation will be described, as well as MEA elaboration and performance and durability in PEM water electrolysis. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2010-2013) for the Fuel Cells and Hydrogen Joint Undertaking under grant agreement Electrohypem no. 300081.

CC.CC.5.2
14:15
Authors : A. Albert, T. J. Schmidt, L. Gubler
Affiliations : Electrochemistry Laboratory, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Resume : Polymer electrolyte electrolysis cell (PEEC) is one of the common types of water electrolyzer. It is commercially available, but due to its high cost it is not yet suitable for large-scale applications. The proton conducting membrane as the electrolyte in a PEEC plays an important role for the efficiency and durability of the system. Nafion membranes are commonly used in PEECs. However, since these perfluorinated materials are expensive, many alternative membranes are investigated. Radiation grafted membranes are one of these alternatives, since their cost is potentially lower and their properties can be readily modified by varying the composition and architecture of the graft copolymer. In this study, radiation grafted membranes with a combination of styrene/acrylonitrile (S/AN) and styrene/acrylonitrile/1,3-diisopropenylbenzene (S/AN/DiPB) as grafting monomers were synthesized and compared to Nafion membranes and α-methylstyrene/methacrylonitrile (AMS/MAN) co-grafted membrane. Since the PEEC and polymer electrolyte fuel cell (PEFC) exhibit the same mechanism of proton conduction in the membrane, it is feasible to investigate the performance and properties of a membrane for the PEEC in a PEFC. A property map and figure of merit are introduced and can be used for evaluating alternative membranes for electrolyzer applications in terms of area resistance and hydrogen crossover. The results show that the radiation grafted membranes are promising alternatives to Nafion.

CC.CC.5.3
14:30
Authors : Tobias Höfner, Marcelo Carmo , Wiebke Maier, Jürgen Mergel, Detlef Stolten
Affiliations : Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Electrochemical Process Engineering, 52425 Jülich, Germany; Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Electrochemical Process Engineering, 52425 Jülich, Germany; Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Electrochemical Process Engineering, 52425 Jülich, Germany; Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Electrochemical Process Engineering, 52425 Jülich, Germany; Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Electrochemical Process Engineering, 52425 Jülich, Germany, Chair for Fuel Cells, RWTH Aachen University, Germany

Resume : Water electrolysis provides a sustainable solution for the production of hydrogen when coupled to renewable power sources such as wind and solar energy. To combine the positive aspects of alkaline and polymer electrolyte membrane (PEM) electrolysis we use anion exchange membranes (AEMs) to develop high performance membrane-electrode-assemblies (MEAs). In this study electrochemical impedance spectroscopy (EIS) was applied to evaluate the ionic conductivity of commercial AEMs. In order to determine the hydrogen crossover rate through the membrane, we developed an advanced electrochemical cell setup. Commercial catalysts were screened on a rotating disc electrode in order to identify potential noble metal-free catalysts for the AEM water electrolysis. Catalysts were coated on the membrane via spray coating to obtain MEAs for a new generation of water electrolysers. Based on these results, we demonstrate MEAs with promising activities for the AEM water electrolysis. The membranes we tested showed satisfying ionic conductivities but further steps have to be taken to improve the long term-stability during single cell operation. First hydrogen-crossover analysis showed low hydrogen permeability for the hydrocarbon-type AEM samples compared to perfluorinated Nafion 117.

CC.CC.5.4
14:45
Authors : Christoph Rakousky, Marcelo Carmo, Wiebke Maier, Juergen Mergel, Detlef Stolten
Affiliations : Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany; Forschungszentrum Juelich GmbH, Institute of Energy and Climate Research, IEK-3: Electrochemical Process Engineering, 52425 Juelich, Germany and Chair for Fuel Cells, RWTH Aachen University, Germany

Resume : Different water electrolysis methods are available to produce hydrogen, amongst which the polymer-electrolyte membrane (PEM) electrolysis is most suitable for the coupling to the fluctuating load profiles of renewable energies such as wind or solar. However, conventional PEM electrolyzers depend on scarce and expensive iridium-compounds as electrocatalysts for the oxygen evolution reaction (OER). Therefore one of the challenges lies in reducing the amount of applied iridium metal, e.g. by increasing its utilization, while retaining long-term stability. In order to increase the utilization of Ir, we synthesized OER catalysts employing various support materials, e.g. TiO2 and ATO. The mass activities of Ir-OER catalysts are evaluated using the rotation disk electrode (RDE) approach. In order to determine the optimum amount of sample material on the RDE, a loading variation is performed. These findings are used to determine a benchmark catalyst and set up a performance ranking. Degradation tests with different load profiles are performed for the promising electrocatalysts to investigate their durability and the effect of the load profile on the degradation. Our findings indicate a variation of factor 2 in mass activity within the range of researched RDE-loadings. Our supported Ir-catalysts show 60% higher mass activity and similar degradation behavior compared to the benchmark system. Furthermore we show that the catalyst degradation is dependent on the measurement protocol.

CC.CC.5.5
15:00
Authors : Timothy N. Lambert,* Danae J. Davis, Julian A. Vigil, and Steven Limmer
Affiliations : Department of Materials, Devices, and Energy Technologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, Fax: 505-844-7786; Tel.: 505-284-6967; *Email: tnlambe@sandia.gov

Resume : Reversible oxygen electrochemistry is vital to numerous future renewable energy technologies, such as fuel cells, metal-air batteries, and electrolyzers. Active electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are known; however, they are typically expensive and based on rare materials such as Pt (for ORR) and Ir or IrOx (for OER). These can also suffer from reaction poisoning and poor electrochemical selectivity, further decreasing their utility. Therefore, catalyst materials that are highly active, stable, and cost-effective are needed. We have recently begun developing catalysts for oxygen electrochemistry in aqueous electrolytes. We will present on Cu-α-MnO2 nanowire electrocatalysts and demonstrate how various Cu-ion doping amounts alter the nanowire surface area, crystalline lattice, conductivity, and the manganese oxidation state; we then rationalize how these factors impact the activity for the ORR. We will demonstrate that when blended with a graphene-like carbon, Cu-α-MnO2 compares well to the Pt/C benchmark for the ORR in alkaline electrolyte. We will also present on our new porous Co3O4 and NixCo3-xO4 spinel films. Electrocatalytic data shows performance rivaling that of commercial benchmarks and recent literature catalysts for both the ORR and the OER. These electrocatalysts hold much promise for improving the efficiency of devices reliant on reversible oxygen electrochemistry. This work was supported by Sandia National Laboratories: Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.

CC.CC.5.6
15:15
Authors : Chinmoy ranjan, Zoran Pavlovic, Robert Schloegl
Affiliations : Max Planck Institute for Chemical Energy Conversion

Resume : Non noble metal "earth abundant" electrocatalysts will significantly reduce the costs and make it possible to use electrochemical water splitting (electrolysis) on a very large scale. Non noble metal catalysts can be an effective replacement even if their electrochemical activities are a fraction of their noble metal counterparts. If these catalysts can be developed to an extent where their operational lifetime would become comparable to their noble metal counterparts, a large part of the problem would be solved. MnO2 is earth abundant and well known for catalyzing oxygen evolution. A form of MnOx cluster is known to catalyze water oxidation in photosynthesis. The problem is that the catalyst comes with a significant corrosion problem. Besides that MnO2-xnaturally exists in various polymorphs, with various amounts of defects each of which is known to have a different electrocatalytic performance. Poor ballistic electronic conduction (important for good electrode materials) is also a prevalent issue with these oxides. These catalysts although with immense potential remain a long way from successful implementation within electrolysers. In order to understand the limitations of this catalyst under the operational conditions, it is important to study this material in situ. Setup for in situ Surface Enhanced Raman Spectroscopy is used for tracking the structural changes of hydrous MnOx. Electrodeposition of MnOx on the surface of Au was achieved by passing an anodic current of 50 mC/cm2 at 1,6V. The resulting MnO2 phase could be termed as the alpha/MnO2 phase. The structural integrity of the MnOx was studied by following the Mn-O-Mn stretching various potential ranges in various electrolytes. Onset of phase changes and corrosion could be clearly established. Beside this, other methods such as XRD, SEM, TEM where applied to study these thin films.

CC.CC.5.7
15:30
Authors : J. R. Galan-Mascaros, J. Soriano-López,
Affiliations : Institute of Chemical Research of Catalonia (ICIQ); Catalan Institution for Research and Advanced Studies (ICREA)

Resume : Polyoxometalates, as discreet and molecular counterparts of metal oxides, are excellent candidates for catalytic applications, since they add the chemical characteristics of metal oxides to the easy processing and high activity of homogeneous species. Recently, they have been proposed as candidates for water oxidation catalysis (WOCs) with Earth-abundant metals.[1] In this regard, we have discovered In our group the WOC activity of the nonanuclear {Co9(H2O)6(OH)3(HPO4)2(PW9O34)3}16- (Co9) polyoxometalate.[2] Co9 is an efficient and robust water oxidation catalyst in homogeneous conditions and neutral pH and, furthermore, it has demonstrated to remain active in the solid state.[3] In heterogeneous conditions, Co9 exhibits unparalleled stability and performance when compared even with cobalt oxides, being the first oxide-based WOC active in acidic media. In this communcation we will report the preparation and characterization of large surface area electrodes modified with Co9 to deliver stable and high current density anodes for electrolyzers. [1] H. Lv et al. Chem. Soc. Rev. 2012, 41 7572–7589. [2] S. Goberna-Ferron et al. Inorg. Chem. 2012, 51, 11707–11715. [3] J. Soriano-Lopez et al. Inorg. Chem. 2013, 52, 4753-4755.

CC.CC.5.8
15:45
Authors : Denis Bernsmeier1, Michael Bernicke1, Laemthong Chuenchom1;2, Bernd Smarsly2, Ralph Kraehnert1
Affiliations : 1 Technische Universität Berlin, Berlin, Germany 2 Justus Liebig Universität, Giessen, Germany

Resume : Hydrogen is a promising medium for storage and transport of energy from renewable resources. One way to produce hydrogen is the electrolysis of water. In the so-called Hydrogen Evolution Reaction (HER) H2 molecules are produced at the cathode of electrolytic cells. The most active electrocatalysts for HER under acidic conditions are typically based on Pt as active metal. However, Pt is an expensive and scarce element. We developed a synthesis approach based on nanocasting for mesoporous Pt/C catalyst layers which employs polymer micelles as pore templates. The prepared catalyst layers consist of small Pt nanoparticles (Pt-NP) with a narrow size distribution. The Pt-NP are well-dispersed in an open porous carbon matrix. We employed the ability to systematically tune the structure and composition of these mesoporous Pt/C systems for the investigation of structure-activity relationships in the electro-catalytic HER. Pt/C catalysts were synthesised via dip-coating using resorcinol and formaldehyde as precursor materials and PEO-PPO-PEO polymers of the Pluronics family as structure-directing agents. Platinum nitrate was employed as Pt source. Controlled layer deposition resulted in formation of an ordered mesophase. After thermal removal of the template polymer Pt-NP containing mesoporous catalyst films were obtained. Film parameters like thickness, conductivity, pore size and Pt-content were readily controlled by variation of the respective synthesis parameter.

CC.CC.5.9
16:00 Plenary Session    
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Lithium Batteries : Mike Toney and Stefan Adams
09:15
Authors : Johanna Nelson Weker, Nian Liu, Joy C. Andrews, Yi Cui, Michael F. Toney
Affiliations : Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA Department of Materials Sciences, Stanford University, Stanford, CA

Resume : Germanium has a significantly higher theoretical energy storage capacity (1600 mAhg-1) than the carbon-based anodes (372 mAhg-1) presently used in Li-ion batteries and Ge has relatively high electronic conductivity and room temperature Li-ion diffusivity. Yet large volume changes during operation severely limit Ge anode lifetimes. To understand the dynamics and failure mechanism of these and other electrode materials, it is essential to image batteries under operating conditions. Here we show significant size dependence on the cycling characteristics of micron-sized Ge particles employing hard X-ray microscopy during typical battery operation. We found smaller Ge particles experience volume expansion before their larger counterparts. However, these small particles rapidly lose electrical contact and only the largest particles contribute to the battery capacity in the second cycle. Finally, we found particles with larger surface area to volume ratios have greater volume changes during lithiation. Our results demonstrate the significant value in high resolution imaging of batteries under operating conditions and suggest possible strategies to mitigate capacity fade in Ge and Si anodes.

CC.CC.6.1
09:30
Authors : Biao Zhang, Jang-Kyo Kim*
Affiliations : Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clearwater Bay, Kowloon, Hong Kong

Resume : Freestanding carbon nanofiber (CNF) composite films containing various active materials with multi-functional capabilities are produced via facile electrospinning for anodes in high performance Li ion batteries (LIBs). A systematic study is made of the effect of nitrogen species on the performance of Li ion storage and capacities of CNF-based anodes [1]. When the CNF films are subjected to carbonization, transformation occurs from an amorphous to a graphitic structure with associated reduction of nitrogen-containing functional groups. The carbonization temperature plays an important role in determining the atomic structure and morphology of CNFs. A high temperature treatment promotes graphitization through aromatic growth and increases the electrical conductivity. Defects and heteroatoms are simultaneously removed during the transformation from the amorphous carbon to a graphitic structure at a high temperature with a concomitant reduction in nitrogen content. The structural change strongly affects where the Li ions are stored in the CNF electrodes. It is revealed that Li ions can be stored not only between the graphene layers, but also at the defect sites created by nitrogen functionalization. This finding is mainly responsible for the widely-reported improved electrochemical performance of LIBs due to N-doping of electrode materials. An optimized carbonization temperature of 550 oC is identified which gives rise to a sufficiently high nitrogen content and thus a high capacity of the electrode. Fe sacrificial catalyst is employed to improve the electronic conductivity of CNFs due to its ameliorating effect on enhanced graphitization [2]. The Fe3C particles formed within the CNFs after carbonization are chemically etched to produce CNFs with nanopores covered by graphene layers. The pore size and volume could be tuned by controlling the Fe precursor content. Exceptional capacities and excellent rate performance have been achieved arising from the synergistic effects of (i) functionalization with carbonyl and carboxyl groups, (ii) presence of nanopores and (iii) embedded graphene layers. The synergy stemming from the reactions between the Li ions and the functional groups and the abundance of Li ions accumulated in nanopores results in an exceptional capacity of 983 mAh g-1, along with an excellent rate capability due to the high conductivity. The abundant nanopores mean that metal or metal oxide nanoparticles possessing inherently very high capacities, such as Si and SnO2, can be encapsulated within the pores of CNFs, a potential to deliver even higher capacities and capacity retention. Therefore, SnOx particles are incorporated into the CNFs to further enhance the capacities, in which CNFs can act as buffer layer to alleviate the volume change and provide fast charge transfer paths to achieve both high rate performance and long cyclic life. Sub-nanosized SnOx particles are in situ embedded in the conductive CNF matrix by incorporating Sn(II) 2-ethylhexanoate into the PAN precursor for electrospinning [3]. The amorphous SnOx particles at the atomic scale give rise to an exceptional electrochemical performance of the SnOx/CNF electrodes. These ultrafine particles facilitate the reaction Sn + xLi2O → SnOx + 2xLi+ + 2xe-, making it highly reversible. Exceptionally high capacities of 674 mAh g-1 are achieved after 100 cycles when discharged at 0.5 A g-1. The SnOx particles remain well dispersed within the CNFs even after 100 charge/discharge cycles, confirming the structural stability of the composite electrodes. References: [1] B. Zhang, Y. Yu, Z.L. Xu, S. Abouali, M. Akbari, Y.B. He, F. Kang, J.K. Kim. “Correlation between atomic structure and electrochemical performance of anodes made from electrospun carbon nanofiber films” Adv. Energy Mater. (2014) DOI: 10.1002/aenm.201301448. [2] B. Zhang, Z.L. Xu, Y.B. He, S. Abouali, M. Akbari, F. Kang, J.K. Kim. “Exceptional rate performance of functionalized carbon nanofiber anodes containing nanopores created by (Fe) sacrificial catalyst” Nano Energy (2014) DOI:10.1016/j.nanoen.2013.12.011. [3] B. Zhang, Y. Yu, Z.D. Huang, Y.B. He, D.H. Jang, W.S. Yoon, Y.W. Mai, F. Kang, J.K. Kim. “Exceptional electrochemical performance of freestanding electrospun carbon nanofiber anodes containing ultrafine SnOx particles” Energy Environ. Sci. 5 (2012) 9895-9902.

CC.CC.6.2
09:45
Authors : Michael J. Wagner, Kevin Hays, Nathan Banek
Affiliations : The George Washington University

Resume : Li alloying metals have much greater specific and volumetric energy densities than current state of the art graphite used in commercial Li-ion batteries. However, the extremely large volumetric changes that the metals undergo when alloying with Li lead to the structural degradation of the electrode with consequent poor cycle life. To combat volumetric changes, we have made stable Li alloying Sn electrodes by encapsulating the Sn in hollow carbon nanospheres (HCNS), confining them inside the conductive HCNS matrix with sufficient room to reversibly expand and contract without loss of electrode intergrity. In addition to the encapsulated Sn, the outside of the spheres are also decorated with Sn nanoparticles, utilizing the void space in the packing of the HCNS to maximize the volumetric energy density. HCNS has previously been shown to have excellent high rate and low temperature performance as a Li-ion anode material1. Due to these properties, good electrical conductivity, and a simple synthesis, HCNS is a good candidate for use as an active matrix for Li-alloying metals. The synthesis of HCNS has previously been accomplished using Ni metal nanosphere templates2. Here we describe the synthesis and electrochemical testing of the graphite-like spheres filled with Li alloying metals, specifically NiSn alloy. The synthesis involves laser pyrolysis followed by purification to remove excess metal and amorphous carbon. Initially, Ni and Sn salts are mixed with ground cellulose and pelletized. Next, the material is quickly heated to over 2200 ˚C by a laser, reducing the metal salts to metal nanoparticles and converting the glucosidic polysaccharide to concentric graphene sheets that encapsulate the metal, here termed metal encapsulated HCNS. These spheres are embedded in amorphous carbon with is oxidatively removed by refluxing the material in concentrated HNO3. Sn decoration on HCNS is done by reduction of aqueous SnCl2, using NaBH4. We are currently testing the cycling characteristics of the Sn encapsulated by HCNS and Sn decorated HCNS. Initial cycling test show the Sn encapsulated by HCNS has a discharge capacity of 250 mAh/g electrode, while the Sn decorated HCNS has a capacity of 390 mAh/g with good capacity retention. Currently electrodes with Sn to interior and exterior of HCNS are being tested separately, with the intention of combining them in the future to maximize capacity.

CC.CC.6.3
10:00 Break    
10:30
Authors : C. Andersson1, M. Stiefel1, J. Whitby2, M. Held1, J. Michler2, U. Sennhauser1
Affiliations : 1 Swiss Federal Institute for Materials Science and Technology, Laboratory for Electronics/Metrology/Reliability, Überlandstrasse 129, 8600 Dübendorf, Switzerland 2 Swiss Federal Institute for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkstrasse 39, 3602 Thun, Switzerland

Resume : Examining ageing mechanisms of Li-ion batteries with advanced characterisation techniques to better understand SEI layer formation is important to follow degradation in battery performance. Graphite anodes in three lithium ion rechargeable batteries (APR18650, 1.1Ah nominal capacity) were therefore examined and compared: a pristine cell, a cell which was charged and discharged at 4C (reference cell), and a cell which was fast charged at 10C and discharged at 4C (fast charged cell). The fast charged cell showed a decrease in capacity of over 40%, while the reference cell only displayed a capacity decrease of 10%. Depth profiles from cross-sections produced with Ga-FIB inspected in a He-FIB showed increase in porosity and cracking on the anode for the fast charged cell as compared to the pristine sample. FIB-TOFSIMS measurements show very different materials depth distribution profiles for the pristine and the fast charged cell. Li is located mainly at the surface for the pristine sample whereas it diffuses into the depth of the anode for the fast charged cell. Similar behaviour is found for O and F, where they are confined to the surface in the pristine sample but diffuse into the bulk of the anode in the fast cycled sample. Correlation with the electrical characteristics suggests solid SEI growth through Li insertion into the graphite made possible by cracking of the graphite anode upon ageing, which degrades overall cell capacity for the fast charged battery.

CC.CC.6.4
10:45
Authors : Alexandre Pradon 1, Maria Teresa Caldes 1, Pierre-Emmanuel Petit 1, Camille La Fontaine 2, Stéphanie Belin 2, Erik Elkaim 2, Rémi Dedryvère 3, Erwan Dumont 4, Cécile Tessier 4, Guy Ouvrard 1
Affiliations : 1-Insitut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière BP 32229, 44322 Nantes Cedex 3, France; 2-Synchrotron SOLEIL, l’Orme des Merisiers, Saint-Aubin BP48, 91192 Gif-sur-Yvette cedex; 3-IPREM-ECP (UMR 5254 CNRS), University of Pau, 64053 Pau Cedex 9, France; 4-Saft, 111 boulevard Alfred Daney, 33074 Bordeaux Cedex, France

Resume : Li-rich layered oxides Li1+xM1-xO2 with M = Mn, Co and Ni may be used as positive electrode in Li-ion batteries. The structure of these materials can be described as a stack of two kind of slab: one [LiO6]∞ and one [MO6]∞. Li-excess induces some Li in [MO6]∞ slab and a Li2MnO3-type order appears which probably lead to the extra-capacity [1-2]. Aims of this research are to understand structural and electronic mechanisms occurring in the electrode material during the first cycle at high potential (>4.4V) in order to improve the electrochemical properties (high irreversible capacity, polarization, fading). Our work deals with the influence of (1) the temperature of the 1st cycle and (2) the microstructure on the electrochemical behavior. A combined XRD, TEM and XAS study (ex-situ and operando mode) shows a decrease of the Li2MnO3-type order during the cycle, which mostly disappeared at high temperature. Many stacking faults (in bulk) and spinel-type defects (at edges) were also observed, more at high temperature, which could affected the Li-ion diffusion. We observed at the surface enrichment in Mn, in good agreement with the spinel-type defects. The activation temperature has an influence on the Co and Ni K-edge, whereas the influence of the microstructure is visible only on the Mn K-edge. References: (1) H. Yu et al., the Journal of Physical Chemistry Letters , 4 (2013) 1268 (2) H. Koga et al., Journal of The Electrochemical Society, 160 (2013) A1

CC.CC.6.5
11:00
Authors : Damien Dambournet1, Mathieu Duttine1, Alain Wattiaux2, Etienne Durand2, Alain Demourgues2, Karena Chapman3, Peter Chupas3, Henri Groult1.
Affiliations : 1. UPMC, Sorbonne University, PHENIX Lab UMR CNRS 8234, Paris, France. 2. ICMCB-CNRS, University Bordeaux 1, Pessac, France. 3. X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, USA.

Resume : Iron fluoride provides very appealing redox properties as cathode material such as a high capacity (237 mAh/g for one lithium), a relatively high voltage (around 3.1-3.3V) and a good thermal stability. In this scope, the thermodynamically stable compound β-FeF3.3H2O has been widely used as precursor for the preparation of FeF3. Depending on the method, several types of compounds have been obtained ranging from amorphous to various forms of crystallized compounds. Overall, the decomposition path of the fluoride trihydrate implied an intermediate phase FeF3(H2O)0.33 (referring as the Hexagonal-Tungsten-Bronze type structure) and the thermodynamically stable phase -FeF3 at higher temperature. Precise protocol is required to avoid a phase mixture. Furthermore, two facts have not been clearly understood: (i) the role of structural water on the stabilization of the HTB type structure and (ii) the occurrence of hydrolysis reaction during thermal treatment. Therein, a comprehensive study of the thermal behavior of β-FeF3.3H2O was undertaken by means of thermo-gravimetric analysis combined with mass spectrometry, x-ray diffraction, Pair Distribution Function method, Mössbauer spectroscopy and electrochemical technique. The crystal structure of β-FeF3.3H2O was re-investigated and it thermal decomposition fully described. Our study revealed that the release of the structural water from β-FeF3.3H2O induced the collapse of the structure followed by the concomitant hydrolysis/condensation of the 1D chains of [FeF4(H2O)2]n introducing OH groups in the final phase. A scalable method to prepare a phase pure of the HTB structure will be presented. It structural and electrochemical properties will be reported highlighting the impact of the chemical composition on Li-redox features.

CC.CC.6.6
11:15
Authors : Marketa Zukalova, Barbora Laskova, Arnost Zukal, Milan Bousa, Ladislav Kavan
Affiliations : J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic

Resume : TiO2 (B) is metastable monoclinic modification of titanium dioxide. Zukalova et al. found that Li-insertion into TiO2 (B) is characterized by unusually large faradaic pseudocapacitance. This peculiar effect was ascribed to Li-accommodation in open channels of TiO2 (B) structure allowing fast Li-transport in TiO2 (B) lattice along the b axis (perpendicular to (010) face). Analysis of cyclic voltammograms of Li insertion into TiO2 (B) and anatase provides information about capacitive contributions to overall charge of Li-storage. The enhancement of 30% is found in capacitive contributions (normalized to the total stored charges) in TiO2 (B) compared to that in anatase, in spite of ca. three times smaller surface area of the former. Different charging mechanism explains facilitated Li- insertion in TiO2 (B). The difference is caused mainly by pseudocapacitive Li-storage in the bulk TiO2 (B). Deconvolution of cyclic voltammograms also indicates different capacitive contributions of the two voltammetric peaks, S1 and S2 of TiO2 (B). These results provide novel insight into the Li-storage in TiO2 (B) and its difference from that in anatase. This work was supported by the Grant Agency of the Czech Republic (contract No. 108/12/0814).

CC.CC.6.7
11:30
Authors : D. Safanama,* R. Prasada Rao,* Y. Hu,* N. Sharma,** S. Adams*
Affiliations : * National University of Singapore Department of Materials Science and Engineering;** University of New South Wales, School of Chemistry

Resume : In view of power limitations of organic Li-air batteries, we explore aqueous Li-air batteries with highly soluble discharge products enhancing power performance and energy efficiency, but requiring an electrolyte membrane to prevent a direct contact of Li to the aqueous catholyte. Here we design and test a composite membrane synergizing the robustness of ceramic electrolytes with the flexibility of polymer electrolytes and simplifying design compared to existing multilayer membranes. The optimized membrane contains 70wt% of the NASICON-type high stability electrolyte LAGP (conductivity 5×10^-4 Scm-1) in a polymer matrix of 18wt% PVDF, 6wt% PEO and 6wt% LiBF4. After immersion in acidified 1 M LiCl solution for one month the membrane shows no sign of significant swelling or change in conductivity. An aqueous Li-air cell employing a Li anode, the composite membrane, the catholyte on glass fibre separator and a Pt-impregnated CNT air cathode is constructed and the performance in ambient air is studied. With the LiCl catholyte it showed an open circuit voltage of 3.0 V and the curve has a plateau around 2.9 V (vs. Li). At a constant current density of 1 mAcm-2, the first discharge and charge capacity are 350 and 250 mAh per g of carbon, respectively in the voltage range of 1.0-3.8 (vs. Li/Li+) with low polarization (0.2 V). To investigate the origin of the limited cyclability, the by-products formed during discharge are analyzed by in situ synchrotron studies.

CC.CC.6.8
11:45
Authors : Wei Li,1 Damien Dambournet,1 Henri Groult,1 Olaf J. Borkiewicz,2 Karena Chapman,2 Peter Chupas,2 Delphine Flahaut,3 Marie-Liesse Doublet4
Affiliations : 1 UPMC, Sorbonne University, PHENIX Lab UMR CNRS 8234, Paris, France; 2 X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, USA; 3 Université de Pau et des Pays de l'Adour, IPREM-ECP, CNRS, UMR 5254, Helioparc Pau-Pyrénées, France; 4 Institut Charles GERHARDT, Chimie Théorique, Méthodologies, Modélisation – CNRS, Université Montpellier 2 Montpellier, France

Resume : Owing to their characteristics, lithium ion batteries appeared to be one of the most promising electrochemical devices for energy storage applications. Electrode materials that undergo conversion reactions allow more than one lithium per transition metal to be stored through the formation of metallic nanoparticles (2-3 nm) embedded in a lithiated matrix. However, mechanisms involved in the conversion reactions are extremely complex due to drastic structural rearrangement along with the formation of nanoscaled and/or amorphous particles which are difficult to characterize. Pair distribution function (PDF) analysis allows obtaining structural information within short- and long-range orders. In this study, we employed in situ x-ray PDF recorded during the electrochemical reaction of lithium with CoF2. The experimental data together with first-principles calculations led us to conclude about the co-existence of two different polymorphs of metallic cobalt as conversion products. This differs from the results obtained with other transition-metal compounds, bringing new insights into conversion mechanism. Structural parameters such as phase proportion, lattice parameters as well as particle domains of metallic cobalt were extracted from PDF data, allowing unique atomic details to be obtained.

CC.CC.6.9
12:00 Lunch    
 
Capacitors and Oxides : Charaf Cherkouk
14:00
Authors : Arvinder Singh, Amreesh Chandra
Affiliations : Department of Physics and Meteorology, Indian Institute of Technology Kharagpur, Kharagpur-721302, West Bengal, India

Resume : In the present work, fabrication of an asymmetric supercapacitor (ASC) is reported using MWCNTs/metal sulfide and graphene nanoplatelets as the positive and negative electrodes, respectively. The characterization of the synthesized materials using XRD, SEM, TEM, and XPS data will be presented. The fabricated asymmetric supercapacitor (ACS) device can be charged/ discharged upto1.4 V when both the electrodes are effectively charge balanced. The decoration of metal sulfide nanoparticles on MWCNTs surface simulates additional capacitance and also reduces the entanglement of the MWCNTs. This promotes the ion transportation inside the electrode material and induces higher capacitance. The ASC exhibits a large specific capacitance of ~181 F/g and an ultrahigh energy density of ~49 Wh/kg. In addition, ASC retains ~92 % of its initial capacitance even after 1000 cycles at the specific current of 2 A/g. This makes these SCs a promising candidate for practical applications.

CC.CC.7.1
14:15
Authors : Ece UNUR
Affiliations : Department of Chemistry, Bursa Technical University, Osmangazi 16190, Bursa, Turkey

Resume : Exhaustion of fossil fuel resources entails the use of environmentally friendly renewable energy sources that produce huge amounts of energy. The variable supply of energy and its deposition issues impedes the expansive and efficient use of renewable resources. Supercapacitors, possessing the high energy density of batteries and high power density of traditional capacitors, would overcome the aforementioned energy storage issues. The overall performance of supercapacitors is determined by the embodied energy storage materials. Hierarchically porous carbons prepared by gentle ceramic parogens of two different sizes from an abundant and sustainable source –biomass- offer high storage capacities and discarge-charge rates due to improved specific surface area by the presence of micropores and improved diffusion of charge carriers in matrix by the presence of mesopores. Pseudocapacitance arising from faradaic charge transfer reactions among redox active metal compounds and electrolyte adds to the total capacitance of the carbon substance. Hierarchically porous nanostructured carbons impregnated by redox active metal compounds yield mechanically more stable, high conductivity, thus high capacity electrode materials with high cycling rates and efficiencies.

CC.CC.7.2
14:30
Authors : C.C. H. TRANa, C. DAMASa, A. BENITEZ DE LA TORREb, C. MEDELb, M. CRUZb, J. MORALESb, F. GHAMOUSSa, F. TRAN VANa, A. MERYa, D. FARAHATa, J. SANTOS?PENAa
Affiliations : aLaboratoire de Physicochimie des Mat?riaux et Electrolytes pour l??nergie, Campus de Grandmont, Universit? Fran?ois Rabelais, 37200 Tours (France) bDepartamento de Quimica Inorg?nica e Ingenier?a Qu?mica, Universidad de C?rdoba, Campus de Rabanales, 14071 C?rdoba (Spain)

Resume : Needs of electrochemical energy storage devices have driven great interest in batteries and electrochemical capacitors. Nowadays, RuO2 is the most important oxide-based electrode for electrochemical capacitors. However, ruthenium oxide is quite expensive and other transition metal oxides are currently been investigated as cheaper alternatives. In this context, MnO2 is the most plausible choice [1]. Exploration of these oxides in capacitor devices has shown that, as for RuO2, there is a limited contribution of the electrochemical double layer to the total capacitance, its high value being mostly associated to fast redox reactions taking place at the electrode/electrolyte interface. Therefore, and unlike for traditional carbonaceous materials used as supercapacitor electrodes where the charge storage relies on the electrochemical double layer, the role of mesoporosity in transition metal oxide has been somewhat omitted. In this contribution, we show the synthesis and characterization of mesoporous manganese oxides. Their preparation involved a simple, slow thermal decomposition of an oxalate containing manganese (II) ions [2]. For comparison purposes we have also studied manganese oxide obtained by different original methods including: - the oxidation of alkenes assisted by CTAMnO4 (CTA= cetyltrimethylammonium) [3] - the oxidation of alcohol, dimethylformamide, ethylene glycol, and glycerol by KMnO4 [4,5]. The latter syntheses would lead to micro or macroporous materials with different particles aggregation than found for the mesoporous oxides. We analyzed the effect of mesoporosity on the electrochemical performances of the different systems synthesized, in terms of capacitance, device resistance and cycling efficiency with aqueous electrolytes. Furthermore, influence of the alkenes hydrophobic chain, the counter-ion of MnO4- group, and, in general, of the reductor agent on the morphology of the final manganese oxide are also determined according to specific and porosity determination by BET analysis and SEM imaging. In addition, several electrochemical techniques, including electrochemical impedance spectroscopy and cyclic voltammetry, have been applied for this research to determine electrochemical performances of these different materials. After the study on three electrode cells, such oxides were tested as positive electrodes in front of negative electrodes based on activated carbon. [1] D. B?langer, T. Brousse, J.W. Long, The Electrochemical Society Interface (2008) 49?52. [2] L. Guo, H. Arafune, N. Teramae, Langmuir 29 (2013) 4404?4412. [3] S. Dash, S. Patel, B. K. Mishra, Tetrahedron 65 (2009) 707?739. [4] J-L. Liu, L-Z. Fan, X. Qu. Electrochim. Acta 66 (2012) 302?305. [5] Y-T. Wang, A-H. Lu, W-C. Li. Microp. Mesop. Mater. 153 (2012) 247?253.

CC.CC.7.3
14:45
Authors : Madjid Arab1*, Ali Hallaoui1,2, Abdeljalil Benlhachemin2, Jean Raymond Gavarri1
Affiliations : 1Université du Sud-Toulon Var, IM2NP, UMR CNRS 6242, BP 20132, 83957, La Garde, France 2 Université Ibn Zohr, LME, BP 32/S Agadir, Maroc

Resume : In this study, we develop tungstate materials as electrocatalysts sensors systems allowing the degradation of pollutant. In this work, tungsten trioxide (WO3) was prepared by electrodeposition and used as anode for electrochemical degradation of Rhodamin B dye in aqueous solution. Oxide film was prepared using a facile one-pot chronoamperometry approach, from an electrolytic solution containing an equimolar mixture of Na2WO4.2H2O and H2O2. Several parameters were optimized to deposit these thin films such as the precursor concentration, current density, substrate, time deposit. X- Ray Diffraction (DRX) analyze was used to identified the oxide structure, scanning electron microscopy (SEM) coupled with EDX for morphological studies. The synthesized films were applied for the electrodegradation of organic pollutants by anodic oxidation. The Rhodamin B is deteriorated by electrochemical root using the three-electrode assembly: the working electrode based on WO3 thin film, Platinum foil as counter electrode and saturated calomel electrode as the reference. Many parameters were varied to find the optimal conditions for the degradation (supporting electrolyte, current density, temperature). Ultraviolet spectroscopy and chemical oxygen demand measurements were conducted to follow degradation rate and study the reaction kinetics of Rhodamin B degradation. Keywords: Electrodeposition, Tungsten oxide, Anodic oxidation, Rhodamin B, Reaction kinetics.

CC.CC.7.4
15:00
Authors : D. Marinha (1), E. Dassoneville (1), C. Ogata (2), N. Sergent (2), L. Dessemond (2), C. Tardivat (1)
Affiliations : (1) Laboratoire de Synthése et Fonctionnalisation des Céramiques, UMR 3080 Saint Gobain - CNRS, 550 avenue Alphonse Jauffret, 84306 Cavaillon Cedex; (2) Laboratoire d'Electrochimie et de Physicochimie des Matériaux et Interfaces, UMR 5279, CNR - Grenoble INP - Université de Savoie - Université Joseph Fourier, BP75, 38402 Saint Martin d'Héres, France

Resume : It was recently reported that ceria-based materials are able to perform storage and reduction of NOx at T<300 °C, without need for noble metals. This work proposes to study electrical behavior of Ceria doped or co-doped with Yttria, Titania, Iron and Platinum, under varying temperature and oxygen partial pressure ranges providing context for these results. Ce1-x-yYxMyO2-d where M=Fe, Ti, x=0, 0.20 or 0.25, y=0 or 0.05, were prepared by chemical synthesis. Commercial CGO powder was used as reference material. Impedance spectroscopy measurements were performed from 150 °C to 600 °C at oxygen partial pressures, pO2=1,10-2,10-3,10-5 and 10-21 atm. The main electrical behavior of the samples remained unchanged with doping. Activation energies for conductivity were close to 0.85 eV with predominant ionic conductivity. Similar behavior was observed within 1 to pO2 ranges. At pO2<10-5 atm, the total conductivity increases over one order of magnitude and Ea ~ 0.40 eV, typical of small polaron hopping mechanism. Similar conductivity values indicates that electronic conductivity originates mainly from reduced cerium atoms and not dopants. In order to test the potential for NOx storage and conversion, CGO samples were reduced under H2 gas at 600 °C and then placed under flowing NO2 gas Conductivity drop was measured with time. The experiment was repeated with Ar and identical pO2. It was found that the conductivity drop was faster under NO2, indicating faster re-oxidation kinetics.

CC.CC.7.5
15:15
Authors : C. Cherkouk, M. Zschornak, J. Hanzig, M. Nentwich, F. Meutzner, M. Urena, T. Leisegang, D. C. Meyer
Affiliations : Institut für Experimentelle Physik, Technische Universität Bergakademie Freiberg, Leipziger Straße 23, 09596 Freiberg, Germany Fraunhofer-Technologiezentrum Halbleitermaterialien, Am-St.-Niclas-Schacht 13, 09599 Freiberg

Resume : Unpredictable risk of nuclear power energy and, in particular, the energy turnaround in Germany have renewed interest on green power based energy and material conversion, and solutions for efficient energy storage. Electrochemical energy storage technologies are of particular importance due to high achievable energy densities. Especially all-solid-state batteries, which were previously reserved for low power energy devices, such as microchips, wireless sensors or low-power medical applications, offer greater potential in respect to energy density, safety and autarchic power supply for short and long term operation applications. These aspects and new concepts of electrochemical storage technologies are in the focus of a joint research project – CryPhysConcept – coordinated by the TU Bergakademie Freiberg. This contribution presents a new solid-state battery concept, based on oxide material that aims to use oxygen defect migration in a crystal as electromotive force to store (and release) electric energy. Furthermore, a solid-state air-battery based on thin-film technology containing an oxygen cathode, is addressed in this work. Since the efficiency of metal-air batteries is significantly limited by the activation of oxygen reduction reaction (ORR) as well as of the ion and electron conductivities, an adequate porosity to allow air oxygen to readily diffuse through the cathode material as well as a controlled metal doping is required. The ion implantation of promising transition metal oxides is a key technology to achieve this goal. A co-implanted with Ni2+- and Co2+-ions strontium titanate (SrTiO3) oxide material combined with millisecond flash lamp annealing to create metal clusters, which act as active centres, is used to improve catalytic properties. The depth profile of the samples is characterized by means of Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD). The oxygen catalytic properties of the implanted crystalline SrTiO3 will be demonstrated. FEM-simulations are used to improve functionality.

CC.CC.7.6

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