preview all symposia

ENERGY AND ENVIRONMENT

N

Advanced catalytic materials for (photo)electrochemical energy conversion

Catalysts are widely used to lower thermodynamic barriers and accelerate kinetics of reactions in many (photo)electrochemical energy conversion processes. The past few years have witnessed a rapid growth in catalytic materials research. This symposium aims to bring together researchers who are interested in, and actively working on, catalytic materials and processes for use in (photo)electrochemical energy conversion.

Scope

With the ever-growing deployment of renewable energy and the needs for load-levelling, rapid inter-conversion of electrical energy to chemical energy and vice versa provides an attractive solution to off-peak renewable energy storage and utilization. Using electrolyzers, water can be split producing hydrogen fuels that are clean and high-density energy carriers. Photoelectrochemical (PEC) water splitting using semiconductor photoelectrodes, including multi-junction architectures, offers a straightforward and potentially efficient means of hydrogen production, though formidable challenges for stable and un-assisted water splitting still remain and practical deployment of PEC cells may take a few decades. Electro-fuels, i.e. chemicals produced by electrolyzers, have recently provoked increasing interest: a great deal of work on electrocatalytic and photoelecatalytic CO2 reduction has been reported, and electrosynthesis of ammonia has lately emerged as an alternative to the energy-intensive Haber-Bosch process. As far as fuel cells are concerned, several European countries have announced a timetable for stopping the production and sales of petrol and diesel powered cars. This will open up a huge market for fuel-cell powered vehicles.

To achieve high conversion efficiency, the use of catalysts in (photo)electrolyzers and fuel cells is essential. Remarkable progress has been made in recent years towards the development of new catalytic materials, with particular emphasis on the substitution, either partially or completely, of precious noble metals. Recent advances in in-operando characterization techniques, as well as in theoretical approaches to the prediction of activity trends and catalyst screening allow for fundamental understanding of catalytic mechanisms and processes and rational design of efficient and durable catalytic materials. 

This symposium will provide a platform for researchers working on catalytic materials to showcase and learn about the latest findings in this fast-growing field of research. The symposium covers, but is not limited to, both experimental and theoretical studies of advanced catalytic materials that can find applications in fuel cells and electrolyzers of different types. Contributions to the system design of these (photo)electrochemical energy conversion devices are also welcome.

Hot topics to be covered by the symposium

  • Water splitting and fuel cell catalysts
  • Semiconductor materials including multijunctional/hybrid photoelectrodes
  • Electrochemical and solar-driven CO2 reduction
  • Catalytic materials for electro-fuel and chemical (e.g. methanol, ammonia) synthesis
  • 2D materials for (photo)electrocatalysis
  • Bi-functional and multi-functional electrocatalysts
  • Reduction/replacement of critical metals by nano-design of abundant materials
  • Theoretical and experimental approaches to catalyst screening and design
  • Advanced characterization techniques (in particular in-operando) of photoelectrodes and catalysts
  • Theoretical studies and computational modeling of catalytic mechanisms/processes

List of invited speakers (in alphabetical order):

  • Christian Hess – Technical University of Darmstadt, Germany
  • Foteini Sapountzi – Syngaschem BV, The Netherlands
  • Gongxuan Lu – Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, China
  • Hua Zhang – National University of Singapore, Singapore/City University of Hong Kong
  • Ib Chorkendorff – Technical University of Denmark, Denmark
  • Jingshan Luo – Nankai University, China
  • Juan Ramon Morante – Catalonia Institute for Energy Research (IREC), Spain
  • Ki Tae Nam – Seoul National University, South Korea
  • Laasonen Kari – Aalto University, Finland
  • M. M. Shaijumon – Indian Institute of Science Education and Research Thiruvananthapuram, India
  • Neil V. Rees – University of Birmingham, UK
  • Wolfram Jaegermann – Technical University of Darmstadt, Germany

List of scientific committee members (in alphabetical order):

  • Andy Wain – National Physical Laboratory, UK
  • Byungha Shin, Korea Advanced Institute of Science and Technology, South Korea
  • Enrico Andreoli – Swansea University, UK
  • Grzegorz D. Sulka – Jagiellonian University, Poland
  • Hangxun Xu – University of Science and Technology of China, China
  • Jianwu Sun, Linköping University, Sweden
  • Marc Heggan – Forschungszentrum Juelich, Germany
  • Mihalis Tsampas – Dutch Institute for Fundamental Energy Research (DIFFER), The Netherlands
  • Mingkui Wang – Huazhong University of Science and Technology, China
  • Salvador Eslava, University of Bath, UK
  • Stefano Mezzavilla, Imperial College London, UK
  • Xiaojun Wu – University of Science and Technology of China, China
  • Yujie Xiong – University of Science and Technology of China, China
  • Yung-Jung Hsu – National Chiao-Tung University, Taiwan
  • Yury V. Kolen’ko – International Iberian Nanotechnology Laboratory, Portugal
Start atSubject View AllNum.Add
08:30 Opening remarks    
08:45
Authors : Ib Chorkendorff
Affiliations : Department of Physics, Technical University of Denmark (DTU) Fysikvej, Building 312, DK-2800 Kongens Lyngby, Denmark.

Resume : In this presentation, I will give an overview of some our recent progress in making nanoparticles alloys in relation to electrochemical conversion of sustainable energy [1]. In the first case it will be used to elucidate size dependence and efficiency for catalysts related to the oxygen evolution reaction (OER) which is the limiting reaction and evaluate the scalability of scarce and expensive elements like Platinum and Ruthenium [2, 3]. We shall discuss caveats of testing catalysts for water splitting [4] and investigate size dependence and isotope labelled experiments will be presented for NiFe nanoparticles for oxygen evolution under alkaline conditions [5]. Here we shall demonstrate a new principle for dynamic detection of gas evolution [6] allowing for a clear distinction between redox states and actual OER [7]. Similarly, shall I also touch upon electrochemical ammonia productions – facts or dreams [8]. References [1] Z. W Seh, …, I. Chorkendorff, J. K. Nørskov, T. F. Jaramillo, Science (2017) 355. [2] E. Kemppainen, .. I. Chorkendorff, Energy & Environmental Science, 8 (2015) 2991. [3] E. A. Paoli, F. … I. E.L Stephens, I. Chorkendorff, Chem. Science, 6 (2015) 190. [4] C. Roy, … I. Chorkendorff; Nature Catalysis 1 (2018) 820. [5] J Kibsgaard & I, Chorkendorff, Accepted Nature Energy (2019). [6] D. T. Bøndergaard, I Chorkendorff …Electrochem. Acta 268 (2018) 520. [7] S. Scott, …. I. Chorkendorff. Submitted (2019). [8] S. Z. Andersen, …. And I. Chorkendorff, Accepted Nature (2019).

N.1.1
09:15
Authors : Ki Tae Nam
Affiliations : Department of Materials Science and Engineering, Seoul National University

Resume : Water splitting is regarded as a promising step towards environmentally sustainable energy schemes because electrolysis produces only hydrogen and oxygen, without any by-products. The oxygen evolution reaction (OER), an anodic half-cell reaction, requires extremely high overpotential due to its slow reaction kinetics. In nature, there exists a water oxidation complex (WOC) in photosystem II (PSII) comprised of the Mn and Ca elements. The WOC in PSII, in the form of a cubical Mn4CaO5 cluster, efficiently catalyzes water oxidation with extremely low overpotential value (~160 mV) and a high turnover frequency (TOF) number (~25,000 mmolO2 mol-1Mn s-1). We first identified a new crystal structure, Mn3(PO4)2-3H2O[1], and demonstrated its superior catalytic performance at neutral pH. We revealed that structural flexibility can stabilize Jahn-Teller distorted Mn(III), and thus facilitate Mn redox during catalysis. Additionally, a new pyrophosphate based Mn compound, Li2MnP2O7[2] was studied. We verified the influence of Mn valency and asymmetric geometry on water oxidation catalysis using Li2MnP2O7 and its derivatives. Specific questions that our group intensively focus for the further applications include 1) how we can translate the underlying principles in Mn4CaO5 cluster into the synthetic heterogeneous catalysts and 2) how we can mimic the redox molecule involved biological dark reaction for the CO2 reduction. Toward this vision, we have been developing a new catalytic platform based on sub-10 nm uniform nanoparticles to bridge the gap between atomically defined biological catalysts or their metalloenzyme counterparts and the scalable, electrode depositable heterogeneous catalysts. In this approach, the local atomic geometry is controlled by the nitrogen containing graphitic carbon and the heterogeneous atom doping, that enhance the catalytic activity and selectivity. Additional surface modification by the specific ligand allows for the atomic scale tunability to realize the unique electronic hybridization. References [1] Kyoungsuk Jin, Jimin Park, Joohee Lee, Ki Dong Yang, Gajendra Kumar Pradhan, Uk Sim, Donghyuk Jeong, Hae Lin Jang, Sangbaek Park, Donghun Kim, Nark-Eon Sung, Sun Hee Kim, Seungwu Han, and Ki Tae Nam, J. Am. Chem. Soc. 136, 7435–7443, 2014 [2] Jimin Park, Hyunah Kim, Kyoungsuk Jin, Byung Ju Lee, Yong-Sun Park, Hyungsub Kim, Inchul Park, Ki Dong Yang, Hui-Yun Jeong, Jongsoon Kim, Koo Tak Hong, Ho Won Jang, Kisuk Kang, and Ki Tae Nam, J. Am. Chem. Soc. 136, 4201-4211, 2014

N.2.0
09:45
Authors : Timothy E. Rosser (1), Jo. J. L. Humphrey (1), Junyuan Xu (2), Xian-Kui Wei (3), Marc Heggen (3), Yury V. Kolen’ko (2), and Andrew J. Wain (1)
Affiliations : (1) National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, UK; (2) International Iberian Nanotechnology Laboratory, Braga 4715-330, Portugal; (3) Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.

Resume : Electrochemical water splitting is an attractive means to convert electrical energy into chemical energy, allowing versatile energy storage in the form of hydrogen fuel. However, the technology currently relies on rare and expensive platinum group metals as catalysts, so efforts are underway to develop new catalysts based on more sustainable, earth-abundant materials. In recent years, transition metal phosphides (TMPs) have emerged as alternative catalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Moreover, it has been demonstrated recently that modification of TMPs with Al improves their catalytic activity,[1] but the mechanism behind this improvement is poorly understood. In this work, we explore the phenomenon of Al-induced performance improvement, using cobalt phosphide (denoted here as “Co-P”) in basic solution as an example OER system. Unmodified Co-P and Al-modified Co-P (Al-Co-P) catalysts were prepared via a gas transport phosphorisation route and characterised using HAADF-STEM, EDX mapping and XPS. Al modification results in a favourable shift in OER overpotential, which can be rationalised by an increase in the electrochemical surface area of the catalyst. Operando Raman spectroscopy revealed that Al modification changes the oxidation behaviour of Co-P; in the case of Al-Co-P, Co3O4 is consistently observed under oxidising conditions, whilst this phase is absent in the case of Co-P and instead amorphous CoOx phases are dominant. We speculate that the formation of Co3O4 as a pre-catalyst in Al-Co-P leads to its higher electrochemical surface area compared to Co-P, and hence its apparent improvement in OER performance. [1] J. Xu et al., ACS Catalysis, 2018, 8(3), 2595-2600

N.3.0
10:05
Authors : Bidushi Sarkar, Debanjan Das, and Karuna Kar Nanda
Affiliations : Materials Research Centre, Indian Institute of Science, C. V. Raman Road, Bangalore-560012, India

Resume : Development of eco-friendly, stable and affordable electrocatalysts is crucial for the sustainable energy production and storage units such as fuel cells, water electrolysis, and metal–air batteries. Metal organic frameworks (MOFs) are class of compounds in which metal ions are coordinated to an organic ligand. They have emerged as a great precursor for the synthesis of various electrocatalysts for Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER).[1] Carbon motifs derived from zeolitic imidazole frameworks (ZIFs), a subfamily of MOFs, have exceptional mechanical and chemical stability due to the presence of metal-nitrogen bonds. Amongst various synthesized ZIFs, ZIF-67 has cobalt ions (Co2 ) ions coordinated to imidazolate-type linkers. The ZIF-67 derived nanoporous carbon precursors are generally mesoporous, possess high degree of graphitization and large surface area.[2] Herein, we have tried to immobilize noble metals like Pd, Pt and Ru on ZIF-67 precursor named as PdCo@NC, PtCo@NC and RuCo@NC, respectively. We have synthesized a series of electrocatalysts by a simple one-step pyrolysis. The as-synthesized catalysts show excellent bifunctional catalytic activity towards HER as well as OER in alkaline medium. The catalysts show long cycle stability and compete with the state-of-the-art electrocatalysts like RuO2 and Pt/C. PtCo@NC and RuCo@NC shows the best HER and OER, respectively. Further, the excellent electrocatalytic activity is explained based on a synergistic effect between the noble metal and ZIF-67 derived N-doped carbon support. References [1] J. Liu, D. Zhu, C. Guo, A. Vasileff, S. Qiao, Adv. Energy Mater., 7 (2017), 1700518. [2] X. Cao, C. Tan, M. Sindoro, H. Zhang, Chem. Soc. Rev., 46 (2017), 2660

N.4.0
10:20
Authors : Debanjan Das, Karuna Kar Nanda
Affiliations : Materials Research Centre, Indian Institute of Science, Bangalore-560012, INDIA

Resume : Metal-organic frameworks (MOFs) are a class of porous hybrid solids consisting of metal-containing nodes coordinated with multitopic organic linkers. Recently there has been tremendous interest in the exploration of MOFs and their derivatives for electrocatalysis, however slow charge-transport kinetics often limit the performance. Therefore, making suitable carbon composites would greatly improve their electronic conductivity and subsequently the electrocatalytic activity. Herein, we have developed two different routes using cobalt imidazolate frameworks (ZIF-67) to design cobalt selenide (CoSe) hybridized with nitrogen-doped carbon. The solid-state strategy involves the direct conversion of ZIF-67 into CoSe nanoparticles with an average size of ~20 nm encapsulated within N-doped graphitic carbon shells with an average size of 300 nm. Interestingly, this method can easily be extended to similarly synthesize CoTe encapsulated N-doped graphitic carbon cages by simply changing the precursor. The other method involved the self-templated conversion of ZIF-67 into Co nanoparticles encapsulated N-doped carbon polyhedral and their subsequent transformation into vertically aligned CoSe grafted N-doped carbon sheets via a hydrothermal selenization method. Both, these class of materials so synthesized were found to exhibit excellent electrocatalytic activity towards HER and OER in alkaline medium. It is believed that the methods being developed here may be extended to other transition metal chalcogenides for various applications

N.5.0
10:35 coffee break    
10:55
Authors : Daniel Escalera‐López, Zhiheng Lou, Neil V. Rees
Affiliations : School of Chemical Engineering, University of Birmingham, Birmingham, UK.

Resume : Anodically electrodeposited amorphous molybdenum sulfide (AE‐MoSx) has attracted significant attention as a non‐noble metal electrocatalyst for its high activity toward the hydrogen evolution reaction (HER). The [Mo3S13]2− polymer‐based structure confers a high density of exposed sulfur moieties, widely regarded as the HER active sites. However, their intrinsic complexity conceals full understanding of their exact role in HER catalysis, hampering their full potential for water splitting applications. In this report, a unifying approach is adopted accounting for modifications in the inherent electrochemistry (EC), HER mechanism, and surface species to maximize the AE‐MoSx electroactivity over a broad pH region (0–10). Dramatic enhancements in HER performance by selective electrochemical cycling within reductive (overpotential shift, ηHER ≈ −350 mV) and electro‐oxidative windows (ηHER ≈ −290 mV) are accompanied by highly stable performance in mildly acidic electrolytes. Joint analysis of X‐ray photoelectron spectroscopy, Raman, and EC experiments corroborate the key role of bridging and terminal S ligands as active site generators at low pH, and reveal molybdenum oxysulfides (Mo5+OxSy) to be the most active HER moiety in AE‐MoSx in mildly acidic‐to‐neutral environments. These findings will be extremely beneficial for future tailoring of MoSx materials and their implementation in commercial electrolyzer technologies.

N.6.0
11:25
Authors : Yury V. Kolen’ko
Affiliations : International Iberian Nanotechnology Laboratory, Av. Mestre José Veiga, 4715-330 Braga, Portugal; e-mail: yury.kolenko@inl.int

Resume : Hydrogen plays an important role in clean energy technology, complementing intermittent solar/wind power. Remarkably, lightweight hydrogen has the highest specific energy of any known non-nuclear fuel, and it can be used for both energy generation and storage purposes. More importantly, hydrogen is an environmentally friendly fuel, since only energy and water are the end products of the reaction between hydrogen and oxygen, giving rise to the emerging fuel cell technologies and devices. An interesting way to generate hydrogen is offered by water electrolysis, wherein water is simply decomposed to hydrogen and oxygen by applying a voltage bias. Notably, the water electrolysis is a kinetically controlled process characterized by slow charge transfer and insufficient chemical reaction rates, and in reality, a significantly higher overpotential than the standard potential of the water electrolysis (−1.23 V at 25 °C) needs to be applied to drive the reaction. Therefore, electrocatalysts are used to facilitate water electrolysis by reducing the value of the applied overpotential to conduct cathodic water reduction, known as hydrogen evolution reaction, and anodic water oxidation, known as oxygen evolution reaction, which are the key half reactions of electrochemical water splitting. Whereas the best electrocatalysts for water electrolysis are platinum group metals (PGMs), their main drawback is obvious: they are critical and expensive, thus limiting the viability of PGMs for widespread applications. Hence, the current research trend is aiming at searching for alternatives to PGMs. In this talk, I will first introduce transition metal phosphides and borides as an emerging earth-abundant class of electrocatalysts for water electrolysis, followed by our approaches in interface engineering, synthesis, and electrocatalytic understanding. I will then showcase our recent progress in using these electrocatalysts for water reduction and oxidation.

N.7.0
11:45
Authors : Zhi Wei Seh
Affiliations : Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore

Resume : Electrocatalytic hydrogen evolution can enable the sustainable production of molecular hydrogen as a clean energy carrier. In this talk, I will discuss our latest experimental and theoretical work on 2D transition metal carbides, MXenes, as electrocatalysts for hydrogen evolution. We first studied titanium carbide produced by different fluorine-containing etchants and found that those with higher fluorine coverage on the basal plane exhibited lower hydrogen evolution activity. We then controllably prepared molybdenum carbide with very low basal plane fluorine coverage, achieving a geometric current density of 10 mA cm-2 at 189 mV overpotential in acid. More importantly, our results indicate that the oxygen groups on the basal planes of molybdenum carbide MXenes are catalytically active towards hydrogen evolution, unlike in the case of widely studied 2H-phase molybdenum disulfide, in which only the edge sites are primarily active. These results pave the way for the rational design of 2D materials for either hydrogen evolution, when minimal overpotential is desired, or for energy storage, when maximum voltage window is needed.

N.8.0
12:15
Authors : Bidushi Sarkar, Debanjan Das, and Karuna Kar Nandaa
Affiliations : Materials Research Centre, Indian Institute of Science, C.V. Raman Road, Bangalore-560012, India

Resume : Hydrogen is a clean and zero carbon emission fuel which can be generated via water splitting [1]. However, it requires eco-friendly and inexpensive electrocatalysts to drive the thermodynamically uphill hydrogen evolution reaction (HER). Metal organic frameworks (MOFs) have emerged as an ideal precursor for the synthesis of various electrocatalysts for HER. As a subfamily of MOFs, zeolitic imidazole frameworks (ZIFs) and the carbon motifs derived thereof, can act as potential heterogenous support for immobilizing metals owing to their large surface area, porous structures and feasible catalytically active sites [2]. Herein, we have immobilized monodispersed ruthenium nanoparticles (~ 2 nm) on hollow carbon nanocages (~ 200 nm) by one-step pyrolysis where ZIF-8 is used as the source of carbon nanocages (Ru@NC). The as-synthesized catalyst shows enhanced catalytic activity toward HER in acidic, alkaline as well as neutral medium competing with the state-of-the-art Pt-C catalyst. To study the role of nitrogen-doped carbon nanocages in the catalytic activity, control experiments are performed with ruthenium dispersed on melamine derived carbon (Ru@M) and carbon black (Ru@CB). It is found that Ru@NC outperforms the catalytic activity of Ru@M and Ru@CB at all pH values. This signifies that the catalytic activity is inherently due to synergistic effect between Ru nanoparticles and nitrogen doped hollow carbon nanocages. The chronoamperometry studies show that Ru@NC is stable up to 8 h in all the media. The method developed here can serve as a guideline for future development of related highly active catalyst which may find application in various energy conversion devices. References [1] B. Sarkar, B. K. Barman, K. K. Nanda, ACS Applied Energy Materials, 2018, 3, 1116-1126 [2] T. Liu, P. Li, N. Yao, G. Cheng, S. Chen, W. Luo, Y. Yin, Angew. Chem. Int. Ed. 2019, 58, 4679-4685

N.9.0
12:30 Lunch Break    
14:00
Authors : Jingshan Luo
Affiliations : Institute of Photoelectronic Thin Film Devices and Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China

Resume : Solar fuel production via artificial photosynthesis is considered as one of the most promising strategies to store solar energy. In this symposium, I will talk about our recent works on solar water splitting and CO2 reduction in both photoelectrochemical (PEC) and photovoltaic (PV) approaches. In the PEC approach, we obtained Cu2O photocathodes with a photocurrent density of 10 mA cm-2 and an onset potential of 1 V versus reversible hydrogen electrode by marrying nanowire electrode structure and Ga2O3 buffer layer. In addition, we constructed an all-oxide unassisted solar water splitting device with the BiVO4 photoanode, achieving ~3% solar-to-hydrogen conversion efficiency. In the PV approach, we built artificial photosynthesis systems for solar driven water splitting and CO2 reduction with solar-to-fuel efficiencies exceeding 10% by coupling PV cells with catalyst electrodes. Our results provide rational design strategies for making efficient photoelectrodes and photosystems for solar fuel production.

N.10.0
14:30
Authors : Salvador Eslava, Miriam Regue, Dominic Walsh, Jifang Zhang, Isabella Poli, Ulrich Hintermair, Petra J. Cameron
Affiliations : Department of Chemical Engineering, University of Bath, UK Department of Chemistry, University of Bath, UK. Centre for Sustainable Chemical Technologies, University of Bath, UK.

Resume : Photoelectrochemical solar water splitting offers a clean solution to the world energy requirements of a sustainable future. Achieving its full potential depends on developing inexpensive photoanodes that can efficiently evolve oxygen from aqueous electrolytes, the most kinetically demanding step in water splitting. Here I present recent developments we have achieved in the preparation of inexpensive photoanodes: a nanostructured TiO2 with exposed {0 1 0} facets [1], an α-Fe2O3 self-coated with FeOx electrocatalyst [2] and with an electrodeposited CoFeOx [3], and a novel all-inorganic halide perovskite CsPbBr3 [4]. The nanostructured TiO2 photoanodes are prepared using Ti7O4(OEt)20 clusters as a precursor and resulting photoanodes show a unique morphology resembling desert roses, pure anatase phase and high exposure of the very active {0 1 0} facet, achieving remarkable ⁓100% IPCE efficiency at 350 nm wavelength [1]. α-Fe2O3 photoanodes simultaneously coated with FeOx electrocatalyst are prepared using precursors whose morphology and crystallinity is tuned with lactic acid additive, boosting photoanode photocurrents from 0.32 to 1.39 mA cm-2 at 1.23 V (vs. RHE) [2]. An extended electrochemical characterisation also shows that the charge transfer to electrolyte at α-Fe2O3 interfaces can be boosted by an extremely thin layer of CoFeOx, unlike less thin CoFeOx layers that just reduces surface recombination due to self-oxidation [3]. Finally, all-inorganic halide perovskite CsPbBr3 photoanodes are prepared using carbon as a hole transport layer [4]. This type of semiconductor is revolutionising the field of solar cells due to their high efficiencies and inexpensive preparation but remain practically unexplored in applications using aqueous electrolytes. However, our developed inexpensive carbon layers effectively protect the halide perovskite for more than 30 h directly immersed in water, evolving oxygen with a Faradaic efficiency of 82% and achieving photocurrents above 2 mA cm−2 at 1.23 V (vs. RHE). [1] M. Regue, S. Sibby, I. Y. Ahmet, D. Friedrich, F.F. Abdi, A. L. Johnson, S. Eslava, submitted, 2019 [2] D. Walsh, J. Zhang, M. Regue, R. Dassanayake, S. Eslava, ACS Appl. Energy Mater. 2019, 2, 2043–2052 [3] J. Zhang, R. García-Rodríguez, P. Cameron, S. Eslava, Energy Environ. Sci. 2018,11, 2972-2984 [4] I. Poli, U. Hintermair, M. Regue, S. Kumar, E.V. Sackville, J. Baker, T.M. Watson, S. Eslava, P.J. Cameron, Nature Communications 2019, 10, 2097

N.11.0
14:50
Authors : Mi Gyoung Lee, Ho Won Jang
Affiliations : Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University

Resume : Widespread application of solar water splitting for energy conversion is largely dependent on the progress in developing not only efficient but also cheap and scalable photoelectrodes. Metal oxides, which can be deposited with facile technique and are relatively cheap, are particularly interesting, but high photoactivities is still hindered by the severe charge recombination and the following short life time. Here, two types of heterogeneous TiO2/BiVO4 nanostructures with different band structures, followed by the morphology control of TiO2 are studied. Surface control of TiO2 as a bottom material has a crucial impact on determining the final architecture of electrodes and its photoelectrochemical efficiencies (increased charge separation and prolonged life time). The enhancement in carrier life time of BiVO4/TiO2 nanoflowers is found to be caused by reduction of significant charge carrier recombination via interface control between photoelectrodes. In other words, the morphology modification is affected to the band position of bottom electrodes for forceful water splitting reaction. Overall, these findings provide further insights on the interplay between surface morphology and interface modulation of photoelectrodes, which benefit development of low-cost, highly efficient solar energy conversion devices.

N.12.0
15:05
Authors : Marjan Saeidi1, Amin Yourdkhani1, Seyyed Ali Seyyed Ebrahimi2, Reza Poursalehi1
Affiliations : 1 Materials Engineering Department, Faculty of Engineering, Tarbiat Modares University, Tehran, Iran; 2 Materials and Metallurgical Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran

Resume : Nowadays, using fossil fuels encounters human life serious dangers with environmental crises and climate change. Hydrogen generation by photoelectrochemical water splitting could be a prime solution for these problems. Metal oxide semiconductors are important candidates to be implemented as anodes in photoelectrochemical cells. One of the most important metal oxides on Earth is iron oxide, especially hematite. The combination of a small band gap and significant light absorption, low cost, great abundance and stability in aqueous chemical solution has made it ideal for water splitting applications. In this research, hematite thin films with different thicknesses were grown by liquid phase deposition on fluorine-doped tin oxide (FTO) coated glass substrates at 60 °C and different deposition times followed by annealing at 550 °C for 2 hours. The band gap energy of the films were measured about 1.6 eV. The highest current density of 0.007 mA/cm2 at 1 V RHE potential was obtained for the films with 680 nm. However, small charge carrier concentration limits its applicability. So, the hematite thin films were doped by titanium to improve the photocurrent density. The highest current density of 0.05 mA/cm2 at 1 V RHE potential was obtained for the 4%Ti-Fe2O3 films. Our results indicate that photoelectrochemical properties are thickness and doping dependent in a way that titanium doping enhances the current density.

N.13.0
15:20
Authors : Bartosz Maranowski (a#), Stephane Dulovic (b), Sophia Casto (b), Marcin Strawski (a*), Justyna Widera-Kalinowska (b), Marek Szklarczyk (a)
Affiliations : (a) Laboratory of Electrochemistry, Faculty of Chemistry, University of Warsaw, ul. Pasteura 1, 02-093 Warsaw, Poland (b) Adelphi University, Department of Chemistry, 1 South Avenue, Garden City, New York 11530, United States (#) Starfax Medical, ul. Mickiewicza 25 Warszawa 01-551 Poland

Resume : The goal of this work was to synthesizes photoactive composites made of cadmium selenide and o-methoxyaniline (POMA) by electrochemical deposition method. The deposition was carried out in different ways; a. first CdSe film was deposited and then POMA film, b. first POMA film was deposited and then CdSe film and 3. the CdSe and POMA were deposited simultaneously forming bulk mixture. The fabricated composites were characterized for their chemical stability, magnitude of photo response and width of bandgap. The observed differences were are explained on the basis chemical analysis data (XPS and Raman spectroscopy) and microscopic ones (AFM and SEM data). The width of bandgap was determined by UV-Vis technique. Our research allow for; - Selection of a suitable substrate for the deposition of CdSe and polymer from Au, Pt and HOPG materials. - Selection of a suitable conductive polymer from the group of polyaniline derivatives. - Selection of appropriate synthesis conditions. The research has showed that the most attractive system for photo application is composite obtained when first CdSe film was deposited and then POMA film onto HOPG substrate surface.

N.14.0
15:35 coffee break    
16:00
Authors : Wolfram Jaegermann
Affiliations : Surface Science Divsion, Materialwissenschaft, TU Darmstadt

Resume : For an effective conversion of solar energy to a chemical fuel a lot of different materials as well as device structures have been suggested but only very few provide technological competitive conversion efficiencies. Limitations and loss processes can be deduced from a detailed consideration of the involved photovoltaic and electrochemical elementary steps. These elementary processes as well as their coupling to each other must be optimized without severe losses in the number and the chemical potential of the originally generated electron-hole pairs. We will discuss in this contribution the specific electronic bulk and surface conditions which must be fulfilled to reach high performance: The electronic properties of the absorber materials and their surface properties must be designed according to photovoltaic boundary conditions. Subsequently, H2 and O2 from H2O must be formed by electron and hole transfer reactions with minimized loss of chemical potential. For this purpose the electronic properties of the absorber materials and their interfaces must allow to stabilize the intermediates of the involved multi-electron transfer reaction avoiding unfavourable surface states. This will only be possible if the involved charge transfer steps are coupled to selective multi electron transfer catalysts without loss in the chemical potential of the minority carriers and their photocurrent. Technologically feasible solutions seem to be possible for water splitting and H2-generation, as we will show with a number of investigations performed recently combining electrochemical investigations with surface science studies. Especially our photoemission results on the demands on the bulk and surface electronic structure provides clear boundary conditions on the material’s and surface properties: i) the semiconductors must provide a wide splitting of quasi Fermi levels which seems not possible for oxides with localized electron states as e. g. hematite due to polaron formation. ii) the bonding of H2O and their intermediates directly onto the light energy converting semiconductor surfaces must be avoided because of inherently formed surface states. As a consequence a buried junction is needed. iii) Interface potential drops within the buried junction e. g. between the active PV and the electrocatalyst of the cell may strongly reduce the operative potential at the catalyst`s surface which also lead to severe operative photovoltage losses. Overall it becomes clear that highly efficient and competitive cells need detailed optimizations of device designs in a combination of promising PV absorber materials and adjusted surface passivation layers and electrocatalysts.

N.15.0
16:30
Authors : Grzegorz D. Sulka, Karolina Syrek, Joanna Kapusta-Kołodziej, Leszek Zaraska, Marta Zych, Karolina Gawlak, Krystyna Mika, Monika Sołtys
Affiliations : Jagiellonian University, Faculty of Chemistry, Department of Physical Chemistry and Electrochemistry, Gronostajowa 2, 30387 Krakow, Poland

Resume : Nanostructured semiconductor metal oxides has recently gained considerable attention due to their intrinsic properties such as a high surface area, short solid state diffusion path, high aspect ratio (1D materials), fast electron separation and transport. They are commonly considered as materials for clean energy generation and storage using photovoltaic, photoelectrochemical water splitting, photocatalytic, fuel cell devices, batteries and supercapacitors. Recently, anodization of metals has been adapted for formation of nanostructured oxide semiconductors such as TiO2, WO3, Fe2O3, SnO2 and others. By controlling parameters of the electrochemical oxidation, especially the applied anodizing potential, temperature, electrolyte composition and the process duration, a great variety of unique oxide structures with different morphologies and characteristic parameters can be obtained. Here, we presented some data on the photoelectrochemical properties of nanostructured anodic metal oxides. Semiconducting properties of those oxides, especially band gap energy values, were studied by using UV-Vis reflectance spectroscopy and electrochemical techniques. Photoelectrochemical measurements were carried out using a potentiostat in a three-electrode cell where anodic oxide photoanodes were used as working electrodes. A correlation of the semiconducting behavior with the morphology, structure and composition of anodic oxides was performed. Acknowledgements This work was partially supported by National Science Centre, Poland (Project No. 2016/23/B/ST5/00790).

N.16.0
16:50
Authors : O. A. Krysiak(1,2), J. R. C. Junqueira(1), F. Conzuelo(1), T. Bobrowski(1), A. Wysmolek(3), W. Schuhmann(1)
Affiliations : 1 Analytical Chemistry - Center for Electrochemical Sciences (CES), Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany 2 College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland 3 Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland

Resume : Photoelectrochemical water oxidation has attracted a lot of attention as a renewable and environmentally friendly method for hydrogen production. Due to the fact that the rate determining step in solar-driven water splitting is the oxygen evolution reaction, most of the research focuses on the fabrication of improved photoanodes. For that, semiconducting oxides, which are efficiently absorbing visible light and are resistant to photocorrosion in aqueous solutions, combined with an oxygen evolution catalyst are the state of the art. Although a wide range of catalysts is known, used, and had been tested, the photoelectrocatalytic activity of such composite electrodes is difficult to predict. Many experimental results suggest the existence of compatibility between photoabsorber and catalyst as a prerequisite for improved photocurrents. However, the mechanism of the underlying processes leading to the observed synergy is often unknown. Evidently, a large number of different parameters may influence the photoelectrocatalytic activity and their complex interplay is often not known. In order to contribute to this topic, we examined a set of different transition metal-based catalysts in combination with various photoanodes in two distinct configurations, namely i) with the catalyst deposited on top and ii) embedded inside the semiconductor film. The obtained photoanodes were characterised by means of physical and (photo)electrochemical mea¬surements. The obtained results demonstrate that the interface formed between the photoactive semiconductor and the catalyst plays a decisive role in photoelectrocatalytic activity.

N.17.0
17:05
Authors : Yu-Ting Wang, Yung-Jung Hsu*
Affiliations : Department of Material Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan

Resume : The distribution of solar spectrum is about 6.8% of ultraviolet light (< 400 nm), 38.9 % of visible light (400-700 nm) and 54.3 % of near-infrared light (700-3000 nm). How to extend the photoresponse of semiconductor nanostructures to visible and even near-infrared region is an important task for the advancement of photocatalyst technology. Au nanoparticles have been known as visible sensitizer for wide bandgap semiconductor like TiO2 by virtue of the distinctive surface plasmon resonance absorption. On the other hand, Cu2-xSe nanostructures with Cu vacancies serving as hole donors are capable of effective near-infrared absorption, the introduction of which may also extend the photoresponse of TiO2. In this work, Au@Cu2-xSe nanoparticles were deposited on TiO2 nanowires arrays to demonstrate the extensive photoresponse for photoelectrochemical water splitting. Due to the relative energy band structure, the electron-hole pairs generated in the TiO2-Au@Cu2-xSe composite nanowires can be spatially separated to render efficient carrier utilization. The decorated Au and Cu2-xSe further equipped TiO2 with extended photoactivity toward visible and near-infrared regions. These synergies make TiO2-Au@Cu2-xSe a promising photoanode paradigm for remarkable photoelectrochemical water splitting.

N.18.0
17:20
Authors : Chun-Wen Tsao and Yung-Jung Hsu*
Affiliations : Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Tawian

Resume : With the increasing interest in seeking alternative energy sources, using semiconductors as photocatalyst is a promising approach to the realization of renewable energy technology. Here, we have synthesized Au@Cu7S4 yolk@shell nanocrystals with controllable void size and utilized them as the photocatalyst to perform hydrogen production from water splitting. Together with the visible bandgap absorption of Cu7S4 and the charge separation enhancer of Au, the Au@Cu7S4 yolk-shell nanocrystals displayed efficient water splitting activity under solar irradiation, proven to be an emerging photocatalyst paradigm for achieving solar fuel generation.

N.19.0
17:35
Authors : Guicheng Liu, Meng Wang, Feng Ye, Joong Kee Lee, Woochul Yang
Affiliations : Guicheng Liu, Woochul Yang, Department of Physics, Dongguk University; Meng Wang, School of Metallurgical and Ecological Engineering, Univesity of Science and Technology Beijing; Feng Ye, School of energy power and mechanical engineering, North China electric power university; Joong Kee Lee, Center for energy storage research, Korea Institute of Science and Technology

Resume : To increase the electrochemical active surface area of catalyst layers, herein, a cathodic catalyst layer with novel nanofiber micro-structure has been prepared by adjusting the polarity of the dispersion solution and accelerating the formation time of the micro-structure of catalyst layer, for direct methanol fuel cells (DMFCs) with enhanced power density. Water was added into propanol as dispersion solution for preparing catalyst slurry. In the catalyst slurry, owing to its high-molecular polarity, the water phase could collect polar parts of Nafion moleculars, –SO3H, together to form the polar region. Meanwhile, the –CF2– chain with nonpolarity could spread into propanol to for the low-polar region in the slurry. Because of stronger binding force, the polar region is harder to dry, than the low-polar one. During heat-sparying process at operation temperature of 55 oC, the propanol, as major dispersion agent, evaporated first. And after a certain time, the water phase dried. Therefore, the final morphology, nanofiber structure, of microstructure of catalyst layer was depended on the fiber-shape of the water phase. The novel nanofiber microstructure increased the the electrochemical active surface area of catalyst layer, leading to a higher power density than that of the normal one.

N..0
17:35
Authors : Zhiwei Wang, Guang Yang, Chiew Kei Tan, Tam Duy Nguyen, Loo Pin Yeo, Hao Qun Neo, Andrew Clive Grimsdale, Alfred Iing Yoong Tok,*
Affiliations : School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore

Resume : This work demonstrates hierarchical WO3 nanosheet/CdS nanorod (WO3-NS/CdS-NR) arrays as a type-II heterojunction photoanode for efficient photoelectrochemical (PEC) water splitting. Due to the synergistic effect of different constituents in the novel hierarchical structure, WO3-NS/CdS-NR arrays as a photoanode yield a photocurrent density of 5.4 mA cm-2 at 0.8 V versus reversible hydrogen electrode (RHE) under AM 1.5 illumination. This is 12 times that of WO3-NS arrays (0.45 mA cm-2) and 3 times that of CdS-NR arrays (1.85 mA cm-2). In this hybrid WO3-NS/CdS-NR arrays photoanode, the favorable heterojunction between WO3 and CdS enhances the charge separation efficiency and widens the light absorption spectrum. Furthermore, the optimization of the loading amount and size of CdS-NRs allows for a larger specific surface area as well as more effective light scattering, which further improves the PEC performance of WO3-NS/CdS-NR arrays. Finally, the coating of an ultrathin layer of amorphous TiO2 also enhances the photostability of WO3-NS/CdS-NR arrays.

N..0
17:35
Authors : Kaoruho Sakata, Katerina Minhová Macounová, Roman Nebel, Petr Krtil
Affiliations : J. Heyrovsky Institute of Physical Chemistry, Czech Academy of Sciences

Resume : Photocatalytic property of the semiconductor materials is one of the research target which has received a lot of attention recently. It can be applied for water splitting to produce hydrogen, which is being considered as a potential future energy resource. ZnO nanoparticulate materials can be one of the candidate, and in this study they are fabricated using microwave assisted hydrothermal synthesis from mixture of zinc acetate and ammonium solution as mineralizers. Obtained materials are different sized nanoparticulate and their size can be controlled by the pH of precursor solution for the synthesis. For the purpose of assessing the surface reactivity of the different size and condition of the ZnO nanoparticles in electrochemically, the nano particles were obtained with changing the amount of ammonia in precursor solution. ZnO nanoparticles in this study can be determined as single material, and the mechanism of the synthesis for the nanoparticles and their dominant surface orientation was discussed from the viewpoint of the pH in precursor solution. The photoelectrochemical property of the particles were assessed and it was suggested that the photocurrent of ZnO particles were affected by their size and shape, since their dominant surface orientations can be different. The particles with rough corner shaped surface have a trend that their photocurrent is larger than the particles with smaller smooth surface.

N.20.0
17:35
Authors : Alessandra D'Epifanio, Barbara Mecheri, Cadia D'Ottavi, Silvia Licoccia
Affiliations : Department of Chemical Science and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica, 00133 Rome Italy.

Resume : Bioelectrochemical systems (BES) allow harvesting the energy stored in low-value biomasses offering a new and transformative solution for integrated waste treatment and energy and resource recovery. All BES share the same principle in the anode chamber in which biodegradable substrates are oxidized by a unique group of microbes to convert the chemical energy stored in organic substrates to electrical energy during their anaerobic respiration. By diversifying the reaction at the cathode side cathode, different sustainable biotechnologies can be developed by utilizing this in situ current, such as direct power generation (microbial fuel cells, MFCs), and chemical production (microbial electrolysis cells, MECs). In this work, we have carried out an investigation on the use and valorization of wine industry by-products for energy and/or hydrogen harvesting purposes by means of MFC/MEC technology. Single-chamber reactors have been assembled with either platinum or metal-free catalysts based on nanostructured carbon at the cathode side, comparing their performance in terms of electrical power generation and wastewater treatment. The body of results demonstrated that wine waste can be successfully valued by BES treatment. Acknowledgements: This work has been supported by AGER – Agricoltura E Ricerca (Project name BIOVALE, grant n° 2017-2206).

N.23.0
17:35
Authors : Junyuan Xu, Nan Zhang, Lifeng Liu
Affiliations : International Iberian Nanotechnology Laboratory (INL), 4715-330 Braga, Portugal

Resume : Microstructural engineering is an effective approach to improving electrocatalytic activity of a catalyst. Shape-controlled hollow nanostructures represent a class of interesting architectures for use in electrocatalysis, given that they may offer large surface area, preferably exposed active sites, reduced diffusion pathways for both charge and mass transport, as well as enhanced catalytic activity due to the nano-cavity effect. In this contribution, we for the first time report the synthesis of hollow cobalt phosphide nanoparticles with a well-defined octahedral shape (CoP OCHs).[1] The as-synthesized hollow porous CoP octahedron exhibits excellent electrocatalytic performance for both the oxygen evolution reaction (OER) and the methanol oxidation reaction (MOR) in alkaline media, outperforming porous cobalt phosphide sphere as well as the state-of-the-art commercial ruthenium oxide nanoparticle control catalysts. The synthetic strategy reported here can be readily extended to prepare other hollow shape-controlled metal phosphide catalysts. References [1] J. Y. Xu, Y. F. Liu, J. J. Li, I. Amorim, B. S. Zhang, D. H. Xiong, N. Zhang, S. M. Thalluri, J. P. S. Sousa, L. F. Liu J. Mater. Chem. A 2018, 6, 20646-20652.

N.22.0
17:35
Authors : Changda Wang, Shuangming Chen, Li Song
Affiliations : National Synchrotron Radiation Laboratory, CAS Center for Excellence in Nanoscience, University of Science and Technology of China

Resume : Two dimensional (2D) layered materials have attracted much attention, particularly in electrochemical energy storage felds. Ion intercalation is an important way to improve energy storage performance of 2D materials. However dynamic energy storage process in such layered intercalations is rarely studied, mainly due to the lack of effective operando methods. Here we will present operando X-ray absorption fine structure (XAFS) and in-situ Raman measurements on intercalated transition metal carbides/nitrides (MXene) in combination with ex-situ XRD tests. Such characterizations can clearly reveal the dynamitic changes of each elements during the charging/discharging process, confirming their contribution for lithium storage capacity. The stability of intercalated MXene electrode is also in-situ observed and understood [1-2]. Ref: [1] C. D. Wang, H. Xie, S. M. Cheng, B. H. Ge, D. B. Liu, C. Q. Wu, W. J. Xu, W. S. Chu, G. Babu, P. M. Ajayan, L. Song. Adv. Mater. 2018, 1802525. [2] C. D. Wang, S. M. Cheng, H. Xie, S. Q. Wei, C. Q. Wu, L. Song. Adv. Energy Mater. 2018, 1802977.

N.21.0
17:35
Authors : Inga Jonane1, Andris Anspoks1, Arturs Cintins1, Giuliana Aquilanti2, Aleksandr Kalinko3, Roman Chernikov4, Alexei Kuzmin1
Affiliations : 1Institute of Solid State Physics, University of Latvia, Latvia; 2 Synchrotron Elettra, Italy; 3Universitӓt Paderborn, Naturwissenschaftliche Fakultӓt, Department Chemie, Germany; 4DESY Photon Science, Germany

Resume : Copper molybdate (CuMoO4) has been intensively studied due to its diverse functional properties, including thermochromic, piezochromic, tribochromic, photoelectrochemical as well as catalytic and antibacterial. At room temperature and atmospheric pressure CuMoO4 exists in alpha phase with a bright green colour. Its structure is composed of distorted CuO6 octahedra, CuO5 square-pyramids and MoO4 tetrahedra. By applying pressure or decreasing temperature below ~200 K, copper molybdate colour changes to brownish-red due to the first order phase transition from alpha to gamma phase. The gamma phase is built up of distorted CuO6 and MoO6 octahedra. It is possible to affect the p-T diagram of CuMoO4 and, thus, its properties, by a substitution of Cu2+ ions with other divalent ions as Zn2+ or a substitution of Mo6+ with W6+. Note that similar colour change from green to brown occurs in alpha phase upon heating up to about 673 K. In this study, we use X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) to investigate the relationship between structural effects and optical properties of copper molybdate and its solid solutions with tungsten in the wide temperature range from 10 K up to 973 K. While treatment of thermal fluctuations and static disorder in XAS is a complex task, it can be successfully addressed by reverse Monte Carlo (RMC) simulations.

N..0
17:35
Authors : Junyuan Xu, Lifeng Liu
Affiliations : International Iberian Nanotechnology Laboratory (INL)

Resume : In this talk, I will present our recent efforts towards compositional engineering of transition metal phosphide (TMP) electrocatalysts, with an aim to improve their electrocatalytic performance for hydrogen and/or oxygen evolution reactions (HER & OER). I will showcase two examples: 1) Trends in the OER activity of TMP nanoparticles [1]. We have investigated the alkaline OER electrolysis of a series of TMP catalysts and observed a notable trend in OER activity which follows the order of FeP < NiP < CoP < FeNiP < FeCoP < CoNiP < FeCoNiP. 2) RuCoP nanoclusters showing superior HER performance in alkaline solution [2]. The RuCoP clusters were prepared by wet chemical reduction of metal cations followed by a low-temperature phosphorization treatment. When used to catalyze the HER, they show exceptional activity with a very low overpotential (η) of 23 mV to reach -10 mA cm-2 and a high turnover frequency (TOF) value of 3.85 s-1 at η = 100 mV. References: [1] J. Y. Xu, J. J. Li, D. H. Xiong, B. S. Zhang, Y. F. Liu, K. H. Wu, I. Amorim, W. Li, L. F. Liu, Chem. Sci. 2018, 9, 3470. [2] J. Y. Xu, T. F. Liu, J. J. Li, B. Li, Y. F. Liu, B. S. Zhang, D. H. Xiong, I. Amorim, W. Li, L. F. Liu, Energy Environ. Sci. 2018, 11, 1819.

N.25.0
17:35
Authors : Palani Sabhapathy, Indrajit Shown, Wei-Fu Chen, Kuei-Hsien Chen, Li-Chyong Chen
Affiliations : Palani Sabhapathy; Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei-10617, Taiwan. Center for Condensed Matter Sciences, National Taiwan University, Taipei-10617, Taiwan. Department of Chemistry, National Tsing Hua University, Hsinchu-30013, Taiwan. Molecular Science and Technology, Taiwan International Graduate Program, Academia Sinica, Taipei-11529, Taiwan. Indrajit Shown; Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei-10617, Taiwan. Wei-Fu Chen; Center for Condensed Matter Sciences, National Taiwan University, Taipei-10617, Taiwan. Kuei-Hsien Chen; Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei-10617, Taiwan. Li-Chyong Chen; Center for Condensed Matter Sciences, National Taiwan University, Taipei-10617, Taiwan. Center of Atomic Initiative for New Materials, National Taiwan University, Taipei-10617, Taiwan.

Resume : Electrochemical hydrogen generation via the hydrogen evolution reaction (HER) offers a promising solution for a sustainable energy generation. Platinum (Pt) is the best catalysts for HER; however, the high cost of Pt limits its commercial application. Therefore, developing a low-cost metal catalyst for HER is essential for large scale hydrogen production. Recent advances in carbon materials (ex. CNT, GO) have shown their promising future in energy-related electrocatalytic reactions (ex. ORR) especially, after heteroatoms (N, B, P, and S) doping, the catalytic activity enhanced. Specifically, the co-doping of trace transition metals (ex. Co) on heteroatom-doped carbon materials leads to form metal complexes (ex. Co-Nx), showing promising HER activity. However, the activity is still not good enough for commercial application. Herein, we have demonstrated a new HER electrocatalyst based on Co-N4 system. This Co-N4 catalyst prepared by a one-step pyrolysis process using vitamin-B12 and thiourea as a precursor. The as-synthesized catalyst was characterized by XRD, XPS, and XAS. The results indicate that vitamin-B12 has been decomposed at the high-temperature to form new structure (N-Co-C and N-Co-S), which shows excellent HER activity (In acid, the N-Co-S catalyst shows 67.7 mV @ 10 mA cm-2). Furthermore, the density functional theory calculation reveals, this conjugation induces downshift of the d-band center of cobalt. The downshift of d-band center favors the electrochemical desorption of H and leads to a relatively moderate Co−H binding strength, which helps for enhanced hydrogen evolution reaction. The comparison of HER activity and stability of Co-N4 electrocatalyst in all pH electrolytes will be discussed at the meeting.

N..0
17:35
Authors : K. Welter, N. Hamzelui, V. Smirnov, J.-P. Becker, W. Jaegermann, F. Finger
Affiliations : K. Welter 1; N. Hamzelui 1,2; V. Smirnov 1; J.-P. Becker 1,3; W. Jaegermann 4; F. Finger 1 1 Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research – 5 Photovoltaics, 52425 Jülich (Germany) 2 now at: Institute for Power Electronics and Electrical Drives (ISEA), RWTH Aachen University, 52066 Aachen (Germany) 3 now at: Zentrum für Sonnenenergie und Wasserstoff-Forschung Baden-Württemberg, D-70563, Stuttgart, Germany 4 Institute of Material Science, TU Darmstadt, 64287 Darmstadt (Germany)

Resume : Solar water splitting is a promising way to sustainably produce hydrogen, a clean and storable fuel. We recently reported the application of thin-film silicon multijunction photocathodes with a solar-to-hydrogen (STH) efficiency of 9.5%.[1] The photoelectrodes were optimized on a laboratory scale device area ≤1 cm². However, practical applications critically rely on approaches that are scalable to large areas. We developed a modular device that allows the use and comparison of different device components such as catalysts or solar cell technologies for unbiased solar driven water splitting.[2] Both, thin film silicon multi-junctions and crystalline silicon solar modules were integrated as photoelectrodes into the water splitting device and evaluated regarding their solar-to-hydrogen efficiency. The aperture area of the devices was 64 and 243 cm². For both technologies, various concepts of contact interconnects were investigated aiming at a reduction of current and fill factor losses which are critical on large areas. In order to consider the cost-effectiveness of this technology and to replace high performance noble metal based catalyst pairs (Pt/RuO2 or Pt/IrOx), more abundant NiMo (HER) and NiFeOx (OER) compounds were prepared via electrodeposition. With the NiMo/NiFeOx catalyst pair we obtained η(STH) = 5.1% for a 64 cm² size solar cell which outperformed the Pt/IrOx system (η(STH) = 4.8%).[3] [1] F. Urbain, et al., Energy Environ. Sci. 2016, 9, 145. [2] J.-P. Becker, et al., J. Mater. Chem. A 2017, 5, 4818. [3] K. Welter, et al., J. Mater. Chem. A 2018, 6, 15968–15976.

N..0
17:35
Authors : Krzysztof Sielicki, Małgorzata Aleksandrzak, Ewa Mijowska
Affiliations : West Pomeranian University of Technology, Szczecin, Faculty of Chemical Technology and Engineering, Piastow Ave. 42, 71-065 Szczecin, Poland

Resume : Recently we can observe the increasing interest in clean and renewable sources of energy. One of these is hydrogen, which can replace traditional fuels. In the process of obtaining energy, it produces only steam. These facts make hydrogen excellent alternative to fossil fuels and possibly the fuel of the future. In this work, the authors attempt to synthesize material, which can produce hydrogen in photocatalytic water splitting with high performance is proposed. Graphitic carbon nitride (g-C3N4) is well known metal-free photocatalysts, which can absorb the radiation from UV and visible region. Despite its easy one-step synthesis from cheap organic precursors like urea or cyanamide, the material has its own shortcomings: low quantum efficiency or fast recombination of photoinduced electrons [1]. One of popular way to reduce these disadvantages is heterojunction with carbon materials, e.g. metal-organic frameworks (MOF). MOFs are very popular materials due to their unique properties, like high specific surface area and good charge carrier performance. When carbonized, the highly porous carbon material is received [2]. Latterly, MOFs/g-C3N4 based materials have emerged. L. Tian et. al [3] have synthesized ZIF-8/g-C3N4 composite via the three-step method for solar-driven photocatalytic hydrogen evolution. Composite demonstrated efficient utilization of visible light and improvements in charge transportation and redox capability. On the other hand, Pandiaraj et. al [4] used carbonized MOF-5 as a scaffold for g-C3N4 polymerization. Designed electrocatalyst, shown enhanced oxygen reduction reaction (ORR) activity due to commercial Pt catalyst. It has been proved that synergetic effected occurred between mesoporous carbon and g-C3N4. Nitrogen-doped ZIF-8/g-C3N4 composites were used for bisphenol A degradation under visible light irradiation by Y. Gong et. al [5]. In this work, Schottky contact between ZIF-NC and g-C3N4 facilitate the charge separation of g-C3N4. W. Gu et. al [6] in their work successfully synthesized photocatalyst g-C3N4/MIL-101. Precious-metal free material has shown remarkable catalytic performance with high selectivity and H2O2 yield, excellent stability and durability in the whole pH range for ORR, and it was superior to commercial Pt/C catalyst. Therefore, these properties and a lack of knowledge about carbonization time and temperature dependence of MOF-5 photocatalytic properties forced us to our studies. We would like to present our new approach on MOF carbonization and the influence of process parameters onto photocatalytic water splitting of g-C3N4-MOF composite. References: [1] Zhao, Z., Sun, Y. and Dong, F. (2015). Graphitic carbon nitride based nanocomposites: a review. Nanoscale, 7(1), pp.15-37. [2] Zeng, Y., Fu, Z., Chen, H., Liu, C., Liao, S. and Dai, J. (2012). Photo- and thermally induced coloration of a crystalline MOF accompanying electron transfer and long-lived charge separation in a stable host–guest system. Chemical Communications, 48(65), p.8114. [3] Tian, L., Yang, X., Liu, Q., Qu, F. and Tang, H. (2018). Anchoring metal-organic framework nanoparticles on graphitic carbon nitrides for solar-driven photocatalytic hydrogen evolution. Applied Surface Science, 455, pp.403-409. [4] Pandiaraj, S., Aiyappa, H., Banerjee, R. and Kurungot, S. (2014). Post modification of MOF derived carbon via g-C3N4 entrapment for an efficient metal-free oxygen reduction reaction. Chem. Commun., 50(25), pp.3363-3366. [5] Gong, Y., Zhao, X., Zhang, H., Yang, B., Xiao, K., Guo, T., Zhang, J., Shao, H., Wang, Y. and Yu, G. (2018). MOF-derived nitrogen doped carbon modified g-C 3 N 4 heterostructure composite with enhanced photocatalytic activity for bisphenol A degradation with peroxymonosulfate under visible light irradiation. Applied Catalysis B: Environmental, 233, pp.35-45. [6] Gu, W., Hu, L., Li, J. and Wang, E. (2016). Hybrid of g-C3N4 Assisted Metal–Organic Frameworks and Their Derived High-Efficiency Oxygen Reduction Electrocatalyst in the Whole pH Range. ACS Applied Materials & Interfaces, 8(51), pp.35281-35288.

N..0
Start atSubject View AllNum.Add
08:50 Opening remarks    
09:00
Authors : J.R.Morante
Affiliations : Institut de Recerca en Energia de Catalunya (IREC), E-08930 Sant Adrià del Besòs, Spain; Universitat de Barcelona, Barcelona, Spain Email: jrmorante@irec.cat

Resume : Nowadays, it is a key priority to use renewal electricity or solar energy sources combined with H2O and CO2 feedstocks, earth-abundant elements and environmental friendly materials in electrochemical systems for obtaining value-added chemicals and/or fuels. In this contribution, we report on electrochemical system based on flow-cell devices, which by design is integrated, scalable to large areas, and compatible with earth-abundant and cheap photovoltaics and appropriate electro catalysts. A device composed of a photocathode performing the reduction of H2O or CO2 and an optimized dark anode for the oxygen evolution reaction (OER) will be explored. Different catalyst will be analyzed for increasing selectivity and productivity. Besides system design constraints, parameters such as over-potential values or charge transfer resistances are determined as key parameter for the final energy balance and productivity taking cell voltage minimization as main objective. Three-dimensional (3D) metallic foams (NF) will be shown as scaffold material and the coating process adapted for large area electrodes regarding scalability, nanoparticle size and distribution will also discussed. So, it will be presented impressively low over potentials values for the electro-oxidation at high current densities. Examples based on these catalysts will be reported and electrochemical efficiency higher than 85% will be discussed. In summary, the mechanisms and criteria for selecting feasible catalyst for cathode and anode will be presented and discussed as well as the adequate combination of them with the reactor cell design in order to decrease as much as possible the cell voltage for guaranteeing a maximum goodness in these reactors.

N..0
09:30
Authors : Enrico Andreoli
Affiliations : Swansea University, College of Engineering, Energy Safety Research Institute

Resume : Copper foam electrodes are easy to make, effective, and economical substrates for advanced carbon dioxide catalytic materials. Copper metal is known for its unique ability to convert carbon dioxide to hydrocarbons and alcohols, while metal foams boast high surface area and correspondingly high geometric current densities. However, copper foam catalysts suffer from low selectivity and significant overpotentials. Various strategies have been proposed to overcome these limitations. Our work is focused on identifying and understanding the effect of surface modifiers able to facilitate specific catalytic pathways and generate added-value products such as ethylene and propanol.

N..2
09:50
Authors : Wenbo Ju (1); Fuze Jiang (1,2); Huan Ma (1); Zhengyuan Pan (1,3); Yibo Zhao(1,2); Francesco Pagani (1); Daniel Rentsch (1); Jing Wang (1,2); Corsin Battaglia (1)
Affiliations : (1) Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland; (2) Institute of Environmental Engineering, ETH Zurich, Schafmattstrasse 6, 8093 Zurich, Switzerland; (3) School of Light Industry and Engineering, South China University of Technology, 510640 Guangzhou, China

Resume : Earth-abundant Sn/Cu catalysts are highly selective for the electrocatalytic reduction of CO2 to CO in aqueous electrolyte. However, CO2 mass transport limitations, resulting from the low solubility of CO2 in water, so far limit the CO partial current density to about 10 mA·cm-2 [1,2]. To enhance CO2 mass transport, we developed a process to fabricate Sn/Cu-coated polymer nanofiber networks, and demonstrate the materials as gas diffusion electrodes (GDEs) for electrochemically converting gaseous CO2 to CO [3]. The Sn/Cu-coated PVDF (Sn/Cu-PVDF) nanofiber GDEs achieve CO faradaic efficiencies (FEs) above 80 %, and maintain high CO partial current densities of up to 104 mA·cm-2. The Sn/Cu-PVDF GDE remains highly stable during extended operation at -1.0 V for 135 hours, with an average FE for CO of > 85 %. These results represent an important step towards an economically viable pathway to CO2RR. References [1] W. Ju, J. Zeng, K. Bejtka, H. Ma, D. Rentsch, M. Castellino, A. Sacco, C. F. Pirri, C. Battaglia, ACS Appl. Energy Mater. 2019, 2 867 [2] J. Zeng, K. Bejtka, W. Ju, M. Castellini, A. Chiodoni, A. Sacco, M. A. Farkhondehfal, S. Hernandez, D. Rentsch, C. Battaglia, C. F. Pirri, Appl. Cat. B.: Env. 2018, 236, 475 [3] W. Ju, F. Jiang, H. Ma, Z. Pan, Y. Zhao, F. Pagani, D. Rentsch, J. Wang, C. Battaglia, submitted

N..0
10:05
Authors : Ming Ma, Kasper Tipsmark Therkildsen, Sebastian Dalsgaard, Ib Chorkendorff, and Brian Seger*
Affiliations : Surface Physics and Catalysis, Department of Physics, Technical University of Denmark, 2800 Kgs Lyngby, Denmark Siemens A/S, RC-DK SI, Diplomvej 378, 2800 Kgs. Lyngby, Denmark

Resume : The electrocatalytic conversion of CO2 and H2O into fuels and valuable chemicals has gained significant interest as a promising route for the storage of renewable energy and the utilization of the captured CO2. An essential step for achieving commercial-scale applications of this technology is to reduce CO2 selectively at high reaction rates. Here, we present the selective electrocatalytic conversion of CO2 into C2H4 on thin Cu surface in a flow-cell configuration. Cu catalysts were synthesized on a gas diffusion layer by magnetron sputtering, showing an improved catalytic selectivity for C2H4 formation while inhibiting H2 evolution and CH4 formation with increasing current densities in neutral electrolytes. Notably, this thin Cu layer is able to achieve about 44% catalytic selectivity in the electroreduction of CO2 to C2H4 at a current density of 200 mA/cm2 in neutral electrolytes. The elevated current densities are likely able to create a high pH near the catalyst surface, which can reduce the activation energy barrier for the C-C coupling step that is linked to C2H4 formation, accompanying with suppressed catalytic selectivity for H2 and CH4.

N..0
10:20
Authors : Dr. Laura C. Pardo-Perez, Alvaro Diaz-Duque, Dr. Matthew T. Mayer
Affiliations : Nachwuchsgruppe Elektrochemische Umwandlung von CO2, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH

Resume : The electrochemical reduction of carbon dioxide (CO2R) has gained increasing attention as a sustainable pathway for CO2 reutilization and upcycling into added value chemicals. The initial reduction of CO2 (2e-) can yield formate or CO; while the former has been widely accepted as a terminal product incapable of further reduction, CO has been demonstrated to be a key intermediate in the formation of higher reduction products (>2e-) such as hydrocarbons and alcohols. The CO2 and CO binding strength on the metal surface determine the selectivity. Post transition metals like Sn, In, Bi have weak interaction with CO2 and are known to favor formate. Surfaces like Au and Ag that adsorb CO weakly release it as final product, while surfaces like Pt, Ni, Fe and Co that bind CO too strongly are poisoned and unable to further reduce it, suppressing CO2R and favoring HER. Here we present the exploration of bimetallic composites combining late transition metals traditionally known to bind CO strongly and favor HER (MA=Fe, Ni or Co) with post-transition metals (MB= In, Sn or Bi) known to suppress HER. A facile synthetic approach by spin coating of metal precursors in solution to form mixed oxides (MAMBOx) thin films was chosen for the screening of metal combinations and stoichiometries. The mixed oxide thin films are reduced in situ during CO2R electrocatalytic testing, the structural changes induced during reduction are investigated by electron microscopy, XRD and XPS. The influence of metal composition and stoichiometry on CO2 selectivity will be discussed, along with the effect of the structural and morphological changes observed in the composites during in situ reduction.

N..0
10:35 Coffee break    
11:00
Authors : Gongxuan Lu
Affiliations : Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences

Resume : Semiconductor photocatalysts for overall water splitting into H2 and O2 require metal cocatalyst, such as Pt, to catalyze H2 evolution efficiently. However, these metal cocatalysts can also catalyze hydrogen and oxygen recombination to form water. In this work, we found that the pre-adsorbed halogen atom catalyst could inhibit the reverse reaction of water formation from H2 and O2 due to the decrease of adsorption energies of H2 and O2 on Pt. This inhibition was achieved via the occupation of halogen atom on the Pt surface sites, and thereby the adsorption and activation of hydrogen and oxygen molecules were decreased. The occupation difference of halogen atoms leads the different activity for H2 and O2 recombination. By inhibition of water formation reverse reaction, the over-all water splitting over various TiO2 photocatalysts has been achieved. Isotope experiments with D2O and H218O confirmed the over-all water splitting to H2 and O2. This study may help scientist to develop high-efficient photocatalyst for overall water splitting.

N..0
11:30
Authors : Yujie Xiong
Affiliations : Department of Applied Chemistry, University of Science and Technology of China, Hefei, CHINA

Resume : Considering the excessive emission of atmospheric carbon dioxide (CO2) caused by the combustion of fossil fuels, the sunlight-driven CO2 reduction into higher energy chemicals, such as carbon monoxide, formic acid, methanol or methane, offers a more promising approach to alleviate both global warming and energy crisis. Designing new photocatalytic materials for improving the photoconversion efficiency is a promising route to achieve this goal. Despite the invention of a large number of catalytic materials with well-defined structures, their overall efficiency in photocatalysis is still quite limited as the three key steps  light harvesting, charge generation and separation, and charge transfer to surface for redox reactions  have not been substantially improved. To improve each step in the complex process, there is a major trend to develop materials based on inorganic hybrid structures, in which surface and interface engineering holds the promise for boosting the overall efficiency. In this talk, I will demonstrate several different approaches to designing inorganic hybrid structures with improved photocatalytic performance via surface and interface engineering. It is anticipated that this series of works open a new window to rationally designing inorganic hybrid materials for photo-induced applications.

N..0
11:30
Authors : Hangxun Xu
Affiliations : Hefei National Laboratory for Physical Sciences at the Microscale; CAS Key Laboratory of Soft Matter Chemistry; Department of Polymer Science and Engineering; University of Science and Technology of China

Resume : Semiconducting conjugated polymers have emerged as a novel class of photocatalyst for solar-driven water splitting. Compared to their inorganic counterparts, these synthetic conjugated polymers offer great versatility to develop highly efficient photocatalyts with tunable electronic structures for photocatalytic applications. However, conjugated polymers that are able to efficiently split pure water under visible light (>400 nm) still remain to be explored. We show that 1,3-diyne-linked 2D conjugated polymer nanosheets obtained by oxidative coupling of terminal alkynes such as 1,3,5-tris-(4-ethynylphenyl)-benzene (TEPB) and 1,3,5-triethynylbenzene (TEB) are possessing suitable band structures for photocatalytic overall water splitting and can act as highly efficient photocatalysts for splitting pure water (pH~7) into stoichiometric amounts of H2 and O2 under visible light irradiation. Using in situ techniques, we could further elucidate the reaction pathways during the photocatalytic process, providing strong evidence that the water splitting reaction could occur on the surface of polymer photocatalysts. Meanwhile, inspired by natural photosynthesis, Z-scheme photocatalytic systems are very appealing for achieving efficient overall water splitting. We also show the construction of polymer-based van der Waals heterostructures as metal-free Z-scheme photocatalytic systems for overall water splitting using aza-CMP and C2N ultrathin nanosheets as O2-evolving and H2-evolving catalysts, respectively. We believe that our study could provide new insights in design and synthesis of semiconductors that are able to catalyze overall water splitting at neutral pH with sunlight as the only energy input.

N..0
11:50
Authors : Yi-An Chen, Yung-Jung Hsu
Affiliations : Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 30010, Taiwan

Resume : CdS has been researched on photocatalysis for decades by virtue of the favorable band structure for technologically important reactions such as hydrogen evolution. Further performance enhancement can be achieved by introducing Au nanoparticles, which improves both charge carrier separation and light harvesting capability. Moreover, nanocrystals exposing different facets may exhibit distinct catalytic activities due to the variation of surface energy. Approaches by employing nanocrystals with specific exposed facets have been proven effective in optimizing the photocatalytic efficiency. In this work, we have precisely synthesized Au@CdS yolk@shell nanocrystals with various shell morphology, including cube ({100}-bound), octahedron ({111}-bound), rhombic dodecahedron ({110}-bound) and sphere (isotropic facets). The samples were prepared by using Au@Cu2O core@shell nanocrystals as the template, followed by the sulfidation treatment and cation exchange reaction. Due to the nanosized Kirkendall effect, abundant voids were generated and coalesced during the sulfidation process, producing yolk@shell nanocrystals that possessed hollow shells. For yolk@shell nanocrystals, the cavity enclosed by the nanosized shells provided a confined space to facilitate molecular diffusion, promoting homogeneous reaction to enhance the overall catalytic activities. The effect of the exposed facet on the photocatalytic hydrogen evolution for Au@CdS nanocrystals were systematically studied and interpreted in terms of the surface energy of the facet.

N..0
12:05
Authors : Mei-Jing Fang , Yung-Jung Hsu
Affiliations : Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Tawian

Resume : Ammonia borane (NH3BH3) storing 19.6 wt.% of hydrogen has been considered as a practical hydrogen carrier for producing hydrogen by pyrolysis or hydrolysis method. In this work, we demonstrated the use of Au@Cu2O core@shell nanocrystals as a hydrolysis catalyst to produce hydrogen from ammonia borane. Compared to pure Au and pure Cu2O, a significant enhancement in hydrogen production was achieved for Au@Cu2O, illustrating the synergy of Au and Cu2O in enhancing the catalytic activity toward ammonia borane dehydrogenation. The hydrogen production efficiency can be further improved by applying visible light irradiation during the hydrolysis process. This performance improvement was attributed to the superior photocatalytic activity of Au@Cu2O rendered by the significant charge separation at Au/Cu2O interface as well as the plasmonic effect of Au.

N..0
12:15
Authors : Hiroki Tei, Taku Miyakawa, Hiroto Tsurumaki, Naoto Todoroki, Toshimasa Wadayama
Affiliations : Graduate School of Environmental Studies, Tohoku University

Resume : Electrochemical CO2 reduction (ECR) has been widely studied as one of the method to covert CO2 to valuable substances, such as CO and hydrocarbons. Although alloy electrodes exhibit higher ECR properties than pure metal catalysts, influences of alloy surface atomic arrangements and compositions are unclear. We studied ECR properties of Co- and Sn-deposited Au(110) by using online electrochemical mass spectrometry (OLEMS). Au(110) single crystal substrate surface was cleaned by Ar+ sputtering and subsequent annealing at 1073 K in ultra-high vacuum. 0.1 monolayer(ML)-thick of Co and Sn were deposited onto the cleaned substrate by an electron-beam evaporation method at room temperature (denoted as Co/Au(110) and Sn/Au(110)). Then, the samples were transferred without air exposure to an N2-purged glove box and set to a H-type electrochemical cell. After that, the electrochemical cell was connected to the home-made OLEMS system. Linear sweep voltammetry (LSV) was conducted in CO2-saturated 0.1 M KHCO3 solution. During the LSV measurements, ECR products were detected by quadruple mass spectrometry through porous Teflon inserted PEEK-made-tip. The current densities for both the Co/Au(110) and Sn/Au(110) surfaces slightly increased in compared with the clean Au(110). In contrast, the Sn/Au(110) revealed much larger OLEMS ion current for H2 evolution (m/z = 2) with a lower over-potential than the Co/Au(110) and clean Au(110). In contrast, the Co/Au(110) showed larger OLEMS intensity for CO (m/z = 28), while the current for H2 slightly decreased relative to the Au(110). The results demonstrate that slight amount of alloying elements influence on the ECR on the Au(110) and Co is effective to increase ECR for CO evolution.

N..0
12:30 Lunch break    
14:00
Authors : Hua Zhang
Affiliations : Department of Chemistry, City University of Hong Kong, Hong Kong, China.

Resume : In this talk, I will summarize the recent research on the phase engineering of nanomaterials in my group. It includes the first-time synthesis of hexagonal-close packed (hcp) Au nanosheets (AuSSs) on graphene oxide, the first-time synthesis of 4H hexagonal phase Au nanoribbons (NRBs), the synthesis of crystal-phase heterostructured 4H/fcc Au nanorods, the epitaxial growth of metals with novel phases on the aforementioned Au nanostructures, and the synthesis of amorphous/crystalline hetero-phase Pd nanosheets. In addition, the first-time synthesis of 1T'-MoS2 and 1T'-MoSe2 crystals have been achieved. Moreover, the phase transformation of transition metal dichalcogenide nanomaterials during our developed electrochemical Li-intercalation method will also be introduced. Interestingly, the lithiation-induced amorphization of Pd3P2S8 is also achieved. Currently, my group focuses on the (crystal) phase-based properties and applications in catalysis, surface enhanced Raman scattering, waveguide, photothermal therapy, chemical and biosensing, clean energy etc., which we believe are quite unique and very important not only in fundamental studies, but also in practical applications. Importantly, the concepts of crystal-phase heterostructures and hetero-phase nanomaterials are proposed.

N..0
14:30
Authors : Xiaojun Wu
Affiliations : Hefei National Laboratory for Physical Sciences at the Microscale, and School of Chemistry and Material Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China

Resume : Photocatalytic water splitting, which can directly convert sunlight to molecular hydrogen (H2) and oxygen (O2) from water, represents a promising route towards producing clean and renewable energy. Current photocatalysts for overall water splitting, however, still suffer from insufficient stability, low quantum efficiency, and limited tunability in optical and electronic properties. The search for efficient photocatalysts that can directly split pure water under visible light irradiation remains one of the most challenging tasks for solar energy utilization. On the basis of first-principles calculations and topological modelling method, we designed two-dimensional (2D) nanomaterials, i.e. 2D phosphorous allotropes and conjugated microporous polymers, of which the electronic band structure can be tuned by the basic units assembled in the 2D networks.Our results firstly demonstrate that nine 2D phosphorous allotropes and two conjugated microporous polymers have appropriate valence band and covalent band edge, meeting the requirement for the overall water splitting.

N..0
15:30 Coffee break    
16:00
Authors : Manikoth M. Shaijumon
Affiliations : School of Physics, Indian Institute of Science Education and Research Thiruvananthapuram, CET Campus, Sreekaryam, Thiruvananthapuram, Kerala, INDIA 695016

Resume : The discovery of graphene has opened up new horizons in material science research with its unique and spectacular physical, mechanical, electrical and optical properties.1 Graphene research has sparked great interest in a wide range of 2-dimensional layered materials with varying electronic properties. Atomically thin layered transition metal dichalcogenides (TMDs) such as MoS2, WS2, MoSe2 and WSe2 have been emerging as the cutting edge in materials science and engineering, due to their interesting electronic properties.2 These materials open up new opportunities for a variety of applications, including optoelectronics, energy conversion, and catalysis. To realize their potential device applications, it is highly desirable to achieve controllable growth of these layered nanomaterials, with tuneable structure and morphology.3,-6 In this talk, I will first introduce the controlled synthesis technique that we have recently developed for the growth of luminescent quantum dots of TMDs.6 The method could be extended for other layered materials and such tailored materials show exceptional electrocatalytic properties toward hydrogen evolution reaction (HER)7 and oxygen evolution reaction (OER).8 The talk will also present some of our recent efforts on morphological and electrocatalytic studies of chemical vapour deposition (CVD) grown spiral and pyramid-like few-layer TMDs. References 1. A. K. Geim, K. S. Novoselov, Nat. Mater. 2007, 6, 183-191. 2. H. R. Gutiérrez, N. Perea-López, A. L. Elías, A. Berkdemir, B. Wang, R . Lv, F. López-Urías, V. H. Crespi, H. Terrones, M. Terrones, Nano Lett. 2013, 13 (8), 3447-3454. 3. Y. Gong, P. M. Ajayan et al., Nat. Mater., 2014, 13, 1135–1142 4. D. Gopalakrishnan, D. Damien and M. M. Shaijumon, ACS Nano, 2014, 8, 5297-5303. 5. D. Damien, A. Anil, D. Chatterjee and M. M. Shaijumon, J. Mater. Chem. A 2017, 5, 13364-13372. 6. D. Gopalakrishnan, D. Damien, B. Li, H. Gullappalli, V. K. Pillai, P. M. Ajayan, and M. M. Shaijumon, Chem. Commun. 2015, 51, 6293-6296. 7. Prasad, Shaijumon et al., Nanoscale , 2018, 10, 9516-9524 8. R. Prasannachandran, T.V. Vineesh, A. Anil, B. M. Krishna and M. M. Shaijumon, ACS Nano, 2018, 12, 11511-11519

N..0
17:40
Authors : Tae-Yong An, Jude John, Subramani Surendran, Yelyn Sim, Dong-Kyu Lee, Sung Jun Wee, Chan Min Jo, Hyun Kyu Kim, Yujin Chae, Janani Gnanaprakasam, and Uk Sim
Affiliations : Department of Materials Science and Engineering, Chonnam National University, Gwangju 61186, Republic of Korea

Resume : Development of sustainable energy sources is an urgent issue to meet growing demand in world energy consumption. Among the various types of sustainable energy, hydrogen and ammonia are one of the most promising renewable energy sources with a high energy density. The discovery of efficient catalysts represents one of the most important and challenging issues for the implementation of photoelectrochemical (PEC) or electrochemical fuel production. A critical requirement for outstanding catalysts is not only an ability to boost the kinetics of a chemical reaction but also a durability against electrochemical and photo-induced degradation. Generally, precious metals, such as platinum, exhibit superior performance in these requirements; however, high cost of the precious metal is the biggest barrier to widespread commercial use. To address this critical and long-standing technical barrier, I have focused on an intense search for efficient, durable, and inexpensive alternative catalysts. M y research have been concentrated on two subjects; (1) new possibilities of an atomic-scale catalyst as the efficient water splitting catalysts, (2) the electrochemical production of ammonia using metal nitride-based catalysts. (1) Carbon-based nanomaterials have emerged as promising candidate catalyst for HER. The design of carbon-based catalysts represent an important research direction in the search for non-precious, environmentally benign, and corrosion resistant catalysts. Especially, graphene possesses excellent transmittance and superior intrinsic carrier mobility, thus there have been several attempts to use graphene as a catalyst. It has been reported that reduced graphene oxide containing catalytic active materials exhibited improved activity in HER, oxygen evolution reactions, and oxygen reduction reactions. In most cases, the role of carbon materials is limited to an electrical conducting substrate or a supporter that enhances the performance of other decorated active catalysts. There is no report of the application of monolayer graphene to hydrogen production. For the first time, I investigated new possibilities for monolayer graphene as an electrocatalyst for efficient HER and found that atom ic defect engineering such as nitrogen doping through treatment with N2 plasma improved the catalytic activity. This study has also attracted particular interest to the materials and chemical society in that it has demonstrated the role of carbon-based catalysts with comprehensive electrochemical analysis as well as the first demonstration of monolayer graphene as the HER catalyst. (2) The reduction of nitrogen to produce ammonia has been attracting much attention as a renewable energy technology. Ammonia is the basis for many fertilizers and is also considered an energy carrier that can power internal combustion engines, diesel engines, gas turbines, and fuel cells. Traditionally, ammonia has been produced through the Haber-Bosch process, in which atmospheric nitrogen combines with hydrogen at high temperature (350-550?) and high pressure (150-300 bar). This process consumes 1-2% of current global energy production and relies on fossil fuels as an energy source. Reducing the energy input required for this process will reduce CO2 emissions and the corresponding environmental impact. For this reason, developing electrochemical ammonia-production methods under ambient temperature and pressure conditions should significantly reduce the energy input required to produce ammonia. Metal nitrides are an interesting class of materials for electrochemical ammonia synthesis because they may be able to form ammonia through Mars-van Krevelen mechanism. In the mechanism, a surface N atom is reduced to ammonia, leaving behind a vacancy in the metal nitride surface. This vacancy can then be filled by dissolved N2, which can be further hydrogenated releasing ammonia and regenerating the metal nitride surface. Thus, the suggested might also cause a dynamic Faradaic redox reaction to occur at the surface of the electrode. Here, we report on the experimental electrochemical production of ammonia using metal nitride-based catalysts. Upon applying a reducing potential in N2 purge electrolyte, ammonia was detected using a colorimetry assay test and FTIR spectroscopy. VN, ZrN, Mo2N are interesting materials going forward to study for nitrogen reduction to ammonia due to its significant Faradaic efficiency in an aqueous system under ambient conditions.

N..0
17:40
Authors : Mohsen Sheikhzadeha,b, Seyedsina Hejazib, Shiva Mohajerniab, Ondrej Tomanecc, Radek Zborilc, Sohrab Sanjabia, Patrik Schmukib,c,*
Affiliations : aNanomaterials Group, Department of Materials Science and Engineering, Tarbiat Modares University, P.O. Box: 14115-143, Tehran, Iran b Department of Materials Science, Institute for Surface Science and Corrosion WW4-LKO, University of Erlangen-Nuremberg, Martensstraße 7, D-91058 Erlangen, Germany. c Regional Centre of Advanced Technologies and Materials, Palacky University Olomouc, 17. Listopadu 50A, 772 07 Olomouc, Czech Republic.

Resume : In this work, we report on a facile and novel method for decorating titanium dioxide (TiO2) nanotubes with Rh nanonetworks for photocatalytic applications. In a first step, a metallic Ti-Rh (0.2 at%) alloy is etched in kroll’s solution leading to dealloying surface which results in the formation of Rh nanoparticle-networks on the alloy surface. By subsequent anodization of the surface samples, Rh:TiO2 nanotubes can be grown where the tubes mouth are strongly decorated with Rh nanoparticles network (RhNs) as evident from X-ray photoelectron spectroscopy (XPS) analysis. These Rh oxide Ns are converted to metallic Rh under UV irradiation. Here a time dependence increasing H2 evolution from the RhN decorated TiO2 nanotubes is observed under steady state conditions. These nanotubes Rh-decorated by pre-dealloying yield a stable structure providing 5-times higher H2 evolution activity in comparison to nanotubes decorated by conventional sputtering (same loading), and 228 times higher activity than pristine TiO2 nanotubes.

N..0
17:40
Authors : Junyuan Xu, Ana Aráujo, Lifeng Liu*
Affiliations : International Iberian Nanotechnology Laboratory (INL)

Resume : Template-Free Synthesis of Hollow Iron Phosphide–Phosphate Composite Nanotubes for Use as Active and Stable Oxygen Evolution Electrocatalysts Junyuan Xu, Ana Aráujo, Lifeng Liu* International Iberian Nanotechnology Laboratory (INL), 4715-330 Braga, Portugal * lifeng.liu@inl.int Keywords: oxygen evolution reaction, iron phosphide–phosphate, hollow nanotube The oxygen evolution reaction (OER) is a half-cell reaction that is of importance to many electrochemical processes, especially for electrochemical and photoelectrochemical water splitting. Developing efficient, durable, and low-cost OER electrocatalysts comprising Earth-abundant elements has been the focus of electrocatalysis research. We report a cost-effective, scalable, and template-free approach to the fabrication of hollow iron phosphide–phosphate (FeP–FePxOy) composite nanotubes (NTs), which is realized by hydrothermal growth of iron oxy-hydroxide nanorods and a subsequent post phosphorization treatment. [1] When used to catalyze the OER in basic medium, the as-synthesized FeP–FePxOy composite NTs exhibit excellent catalytic activity, delivering the benchmark current density of 10 mA cm–2 at a low overpotential of 280 mV and showing a small Tafel slope of 48 mV dec–1 and a high turnover frequency of 0.10 s–1 at the overpotential of 350 mV. Moreover, the composite NTs demonstrate outstanding long-term stability, capable of catalyzing the OER at 10 mA cm–2 for 42 h without increasing the overpotential, holding substantial potential for use as active and inexpensive anode catalysts in water electrolyzers. References [1] J. Y. Xu, D. H. Xiong, I. Amorim, L. F. Liu ACS Appl. Nano Mater. 2018, 1, 617-624.

N..0
17:40
Authors : Hongliang Jiang, Qun He, Youkui Zhang, Li Song
Affiliations : National Synchrotron Radiation Laboratory, CAS Centre for Excellence in Nanoscience, University of Science and Technology of China

Resume : The precise identification toward active sites of catalysts and the monitoring of product information are highly desirable to understand how the materials catalyze a specific electrocatalytic reaction. With recent developments of in situ and operando characterization techniques, it has been extensively observed that most of the catalysts would undergo structural self-reconstruction as a result of electro-derived oxidation or reduction process of the catalysts at a given potential, often accompanied by the increase or decrease of catalytic activity as well as the change of catalytic selectivity. Here, we will present couple of works regarding structural self-reconstruction of electrocatalysts in several typical electrochemical reactions [1-3]. With this, we hope to provide deep insight into electrocatalysis during dynamitic working process, as well as to offer guidelines for rational design of advanced electrocatalysts. Ref: [1] Zhang Y.K., Wu C.Q., Jiang H.L., Lin Y.X., Liu H.J., He Q., Chen S.M., Duan T., Song L. Atomic Iridium Incorporated in Cobalt Hydroxide for Efficient Oxygen Evolution Catalysis in Neutral Electrolyte. Advanced Materials, 1707522 (2018). [2] Jiang H.L., He Q., Li X.Y., Su X.Z., Zhang Y.K., Chen S.M., Zhang S., Zhang G.B., Jiang J., Luo Y., Ajayan P.M., Song L. Tracking Structural Self-Reconstruction and Identifying True Active Sites toward Cobalt Oxychloride Precatalyst of Oxygen Evolution Reaction. Advanced Materials, 1805127 (2019). [3] Jiang H.L., He Q., Zhang Y.K., Song L. Structural self-reconstruction of catalysts in electrocatalysis. Accounts of Chemical Research, 51, 2968-2977 (2018).

N..0
17:40
Authors : S. Mouli Thalluri, Lifeng Liu
Affiliations : International Iberian Nanotechnology Laboratory (INL)

Resume : p-Silicon has been widely used as a photocathode in solar-driven hydrogen production. However, due to the poor electrochemical stability and sluggish catalytic behavior, a passivation layer and hydrogen evolution reaction (HER) catalysts are usually needed to couple with Si photocathodes, to achieve satisfactory photoelectrochemical (PEC) performance. As opposed to the commonly used Si/passivation layer/catalyst sandwich configuration, we herein report conformal and continuous deposition of a bifunctional cobalt phosphide (Co2P) layer directly on lithography-patterned highly-ordered SiNW arrays and inverted pyramid textured Si wafers [1, 2]. The deposition was realized by drop-casting of Co-containing precursor solutions on Si photocathodes, followed by a low-temperature phosphorization treatment. The conformal and continuous Co2P layer endows dual functions: on the one hand, it serves as a highly-efficient catalyst capable of substantially improving the photoelectrocatalytic activity towards the HER; on the other hand, it can effectively passivate Si protecting it from photo-oxidation, thus prolonging the lifetime of the electrodes. As a consequence, both photocurrent density and operational stability have been substantially improved. The combination of passivation and catalytic functions in a single continuous layer represents a promising strategy for designing high-performance semiconductor photoelectrodes for use in solar-driven water splitting, which may simplify the fabrication procedures and potentially reduce the production cost. References: [1] S.M. Thalluri, J. Borme, K. Yu, et al. Nano Res. 2018, 11, 4823. [2] S.M. Thalluri, B. Wei, R. Thomas, et al. ACS Energy Letters, in revision

N..0
17:40
Authors : Diego N. David-Parra, Deuber L. S. Agostini, Marcos F. S. Teixeira
Affiliations : Sao Paulo State University, Faculty of Science and Technology.

Resume : The development of materials to monitor and minimize negative impacts on the environment and human health has been widely studied. In this sense, the aim of this work was the development of a high performance device for the , built by electrospinning the BiVO4/GO, obtaining through the technique, nanofibers with high surface area when compared with other techniques of deposition. The BiVO4 band gap value (2.4 eV) and its absorption in the visible region (520 nm), together with the high conductivity of the GO, a p-n heterojunction was formed, thus increasing the efficiency of the device, provided optimum results [1]. Optical and Scanning Electron Microscopes (SEM) were able to morphologically confirm the efficiency of the electrospinning technique in the preparation of the BiVO4/GO nanofibers, showing excellent fiber uniformity, no coalescence and obtaining fibers with diameters between 60 and 96 nm. The photoelectrovoltaics measurements showed a significant improvement in the photogenerated current, using the nanofibers, confirmed by the increase of the peak current and the decrease in the value of the peak potential when compared to other methods of preparation already described in literature [2]. In this way, the data corroborate that the union of the photoelectrocatalytic effect of BiVO4/GO and electro-spinning process have a high potential for applications in the field of renewable energy generation. Acknowledgement: CDMF (CEPID/FAPESP) 2013/07296-2, CNPq 159615/2018-6. References: [1] LIU, M., SUZUKI, Y., Current Nanoscience 11 (2015) 499-503 [2] SILVA, M. R., et. al., J Solid State Electrochem 16 (2012) 3267–3274

N..0
17:40
Authors : Sanjay Jatav, Ming-Chao Kao, Matthias Graf, Eric H. Hill
Affiliations : Sanjay Jatav, Institute of Advanced Ceramics, Hamburg University of Technology, 21073 Hamburg Germany; Ming-Chao Kao, Institute of Optical and Electronic Materials, Hamburg University of Technology, 21073 Hamburg Germany; Matthias Graf, Institute of Optical and Electronic Materials, Hamburg University of Technology, 21073 Hamburg Germany; Eric H. Hill, Institute of Advanced Ceramics, Hamburg University of Technology, 21073 Hamburg Germany;

Resume : Fossil fuels are a finite resource that produce emissions which are polluting and warming the planet. However, the sun can be used for water splitting to generate hydrogen and oxygen, which can be used as clean fuels. Towards this end, it has been established that plasmonic metal/ semiconductor heterostructures are promising candidates for visible light driven photocatalysis [1]. Herein we present the colloidal growth of titania, a semiconductor which absorbs in the ultraviolet, in nanoporous gold, a spongelike nanostructured gold network that displays broadband plasmonic absorbance and can catalyze the oxygen evolution reaction [2]. The thickness and homogeneity of the titania grown can be controlled by changing reaction parameters such as pH, surfactant chain length and concentration, and reaction time. Controlled titania growth within the nanoporous gold provides photocatalytic water splitting in the visible spectrum, and a range of structural colors can be produced by the growth of a titania film atop the surface. The purported mechanism for hydrogen evolution in the visible spectrum is plasmon resonance-enhanced injection of hot electrons into titania [3]. References: [1] Ma, Liang, et al. Catalysts 2018, 8(12), 634 [2] Graf, Matthias, et al. Nanoscale 2017, 9(45), 17839-17848 [3] Si, Yuelei, et al. Appl. Cat. B: Env. 2018, 220, 471-476

N..0
17:40
Authors : Vladimir Smirnov 1, Katharina Welter 1, Jan-Philipp Becker 1, Wolfram Jaegermann 2 and Friedhelm Finger 1
Affiliations : 1 IEK-5 Photovoltaik, Forschungszentrum Jülich GmbH, D-52425, Jülich, Germany 2 Institute of Materials Science, TU Darmstadt, D-64287 Darmstadt, Germany

Resume : Photo-electro-catalytic (PEC) water splitting is a promising approach to produce fuels, such as hydrogen,from water using solar energy. An integrated PEC cell consists of a photovoltaic cell (PV) directly combined with an electrolysis cell (EC), where the chemical reactions take place. The efficiency of an integrated PEC device is defined by the solar-to-fuel efficiency, describing the amount of fuel produced by the incident power of the illumination spectrum. In the case of multi-junction Si based solar cells [1], used as photoelectrodes in the present work, annual variations in the solar spectral quality influence the amounts of photogenerated charge carriers in each sub cell. This influences long-term energy conversion, and thus both the photoelectrode and PEC device performance under varied spectral conditions differfrom the performance obtained under standard AM1.5G illumination. Our model accounts for spectral effects in terms of annual variations in illumination for a range of average photon energies of the spectrum. The electrical output of the photoelectrode is combined with the current voltage behavior of the electrolysis, enabling the long-term (annual) performance of the PEC device to be evaluated. We report on the long-term evaluation of the hydrogen production by an integrated PEC device employing various types [1] of multi-junction silicon thin film (STF) solar cells in respect of the influencing parameters.The long-term outputof PEC devices based onthese multi-junction cells is compared and discussed for different catalyst systems based on earth-abundant [2] and precious metal catalysts. [1] F. Urbain, V. Smirnov, J.P. Becker et al, Energy Env. Sci. 2016, 9, 145–154 [2] K. Welter, N.Hamzelui, V. Smirnov et al, J. Mater.Chem. A 2019, 6, 15968-15976

N..0
17:40
Authors : Debanjan Das, Karuna Kar Nanda
Affiliations : Materials Research Centre, Indian Institute of Science, Bangalore-560012, INDIA

Resume : Despite the recent promise of transition metal carbides as non-precious catalysts for hydrogen evolution reaction (HER), their extension to oxygen evolution reaction (OER) in order to achieve the goal of overall water splitting remains a significant challenge. Herein, a new Ni/MoxC (MoC, Mo2C) nanoparticles supported N-doped graphene/CNT hybrid (NC) catalyst is developed via a facile, one-step integrated strategy which can catalyze both the HER and OER in an efficient and robust manner. The catalyst affords low overpotentials of 162 and 328 mV to achieve a current density of 10 mA/cm2 for HER and OER, respectively, in an alkaline medium which either compares favourably or exceeds most of the Mo-based catalysts documented in the literature. The electronic synergistic effect between MoxC, Ni and NC are responsible for the higher electrocatalytic activity wherein, a tandem electron transfer process yields both excellent HER and OER activity. [1] Unfortunately, however, the synergy among the components was curtailed on account of large spatial separation. To mitigate this problem, we pyrolyzed a PANI/NiMoO4 nanowire@rGO hybrid which brought the individual components closer as compared to the previously adopted method resulting in improved catalytic activity. To further enhance the intimacy in these multi-component catalysts, a MOF-confined synthesis method was developed which resulted in the best activity among all the catalysts developed in the series.

N..0
17:40
Authors : Amr Sabbah, Indrajit Shown, Fang‐Yu Fu, Li-Chyong Chen, Kuei-Hsien Chen.
Affiliations : Amr Sabbah MolecularScience and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Tsing Hua University, Taiwan. Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan. Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan. Center for Condensed Matter Sciences, National Taiwan University, Taiwan; Indrajit Shown Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan; Fang‐Yu Fu Center for Condensed Matter Sciences, National Taiwan University, Taiwan; Li-Chyong Chen Center for Condensed Matter Sciences, National Taiwan University, Taiwan; Kuei-Hsien Chen Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan. Center for Condensed Matter Sciences, National Taiwan University, Taiwan.

Resume : Utilization of carbon dioxide conversion to chemical fuels using an artificial photocatalyst under solar irradiation is an ideal goal in renewable energy studies. To date, a variety of strategies have been demonstrated to boost the quantum efficiency of CO2 photoreduction. Coupling of semiconductors considered one of the key challenges to designing a good photocatalyst that can activate the CO2 molecule with smallest possible activation energy and produce selective fuels. Since the activity and selectivity are mainly determined by the suitable band structures and surface states of photocatalysts as well as the photoreaction conditions. In this study, we fabricate ZnS/ZnIn2S4 composite for CO2 reduction under visible light irradiation. When the mass ratio between Zinc and Indium is varied, the composite catalyst shows dramatically increasing of acetaldehyde and methanol formation as major products of CO2 conversion. The optimum ratio exhibits a 200 times enhancement over a single phase of ZnS. The as synthesized samples were characterized by XRD, SEM, TEM, Photoluminescence, UV-Visible diffuse reflectance spectroscopy, XPS, UPS, surface area and CO2 adsorption measurements. Based on the experimental evidence, the interface between both phases is the crucial role of interfacial charge transfer and subsequent enhancing of catalytic activity. In-situ FTIR study has been done to get a deeper insight into the product formation and gain a detailed comprehension of the fundamental reaction steps during the photocatalysis. In conclusion, my presentation will focus on how to efficiently manage the photo-generated charge carriers and surface reactions of semiconductor photocatalysts to boost the photoreduction activity.

N..0
17:40
Authors : T. Merdzhanova, S. N. Agbo, K. Welter, O. Astakhov, V. Smirnov, F. Finger, U. Rau
Affiliations : Institute of Energy and Climate Research (IEK-5)-Photovoltaics Forschungszentrum Jülich GmbH, 52428 Jülich

Resume : Photovoltaic (PV) driven electrochemical (EC) cells can be used for the generation of clean chemical fuels, such as hydrogen. We added a storage battery to this system to investigate how far one could reduce the volatility of PV output by “shaving” peaks of energy production and thereby approach stability requirements e. g. for the electricity distribution grid. A properly matched battery will back up idle periods in PV generation and reduce required peak power of the costly EC part of the system. We have investigated a small scale system that includes a storage battery and an EC cell, together with a multijunction solar cell made of amorphous (a-Si:H) and microcrystalline (μc-Si:H) silicon. In the case of PV-driven water splitting devices, solar-to-hydrogen (STH) efficiencies around 10 % have been achieved with thin-film silicon multijunction solar cells [1]. In the set-up used in the present study, an additional battery is placed in parallel to the EC cell such that the current from the PV device is split between the EC cell and the battery. The energy balance in the system under AM1.5 standard illumination conditions has been investigated with particular focus on how this affects the solar-to-hydrogen (STH), solar-to-battery (STB) and battery-to-hydrogen (BTH) conversion efficiencies. It was observed that the overall system efficiency is strongly dependent on the STH efficiency. The catalysts systems [2] (Ni/Ni and NiFeOX/NiMo) used in the EC cell are found to play a significant role in the power distribution within the entire system. For the Ni/Ni catalyst system the proof-of-concept is demonstrated and the storage battery can be used to power the EC cell in the dark. [1] F. Urbain et al, Energy & Environmental Science 9, 145-154 (2016). [2] K. Welter et al, J. Mater. Chem. A, 6,15968 (2018).

N..0
17:40
Authors : Silvana Eigenmann, Lukas Füglister, Loris Laib and Benno Bucher
Affiliations : HSR Hochschule für Technik Rapperswil, Oberseestrasse 10, 8640 Rapperswil

Resume : Titanium dioxide Ti02 exists in three phases; Rutile with a band gap of 3.0 eV (413 nm), Anatase with 3.2 eV (387 nm), and Brookite with 3.3 eV (376 nm). TiO2 reveals a photocatalytic effect starting with wavelengths below the range of the band gaps. Many applications exists by exploiting the UVA range of sun light. With the advent of UVC LEDs new applications were promised; they are smaller and less delicate than traditional mercury vapor lamps which, in addition, need a high voltage as a source. We investigate the quantum efficiency of the photo catalytic effect of TiO2 with UVC LEDs in water. The wavelength were 265 nm, 285 nm, and 365 nm. The samples of Rutile were prepared under pressure and/or sintered. For Anatase samples doctor blade - method and sintering was employed. The photocatalytic effect of titanium dioxide has been evaluated by the oxidative effect of the hydroxyl radicals produced by the photocatalytic effect. The hydroxyl radicals conversed methylene blue accompanied with a change of the color. A photometer signal determined the decay of the methylene blue in function of time. The resulting properties of the quantum efficiency in function of the wavelengths below 400 nm is still under investigation.

N..0
Start atSubject View AllNum.Add
14:00
Authors : Christian Hess
Affiliations : Eduard-Zintl Institute of Inorganic and Physical Chemistry, TU Darmstadt, Germany

Resume : Understanding the mode of operation of heterogeneous catalysts is of great scientific and economic interest. Such a knowledge based approach strongly relies on the development and application of spectroscopic methods that allow for monitoring the relevant (sub)surface processes under working conditions (operando approach). In this presentation, the potential of combined in situ and operando spectroscopies (IR, Raman, UV-Vis) for direct characterization of adsorbates and the (defect) structure of working heterogeneous catalysts will be illustrated by examples from current research relevant to electrochemical energy conversion. It is shown that the spectroscopic assignment and interpretation of the results is largely facilitated by the use of DFT calculations. Focus will be put on oxide-based materials, including ceria and noble metal doped ceria as a case study; however, approaches for the in situ and operando spectroscopic characterization of carbon-containing materials will also be outlined. Our studies underline that detailed spectroscopic analysis under working conditions of heterogeneous catalysts using combined operando spectroscopies is essential to unravel their mode of operation.

N..0
14:30
Authors : Marc Heggen, Peter Strasser, Rafal E. Dunin-Borkowski
Affiliations : Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany; The Electrochemical Energy, Catalysis and Materials Science Laboratory, Department of Chemistry, TU Berlin, 10623 Berlin, Germany

Resume : Pt-alloy nanoparticles (NPs) with octahedral shapes are attractive as fuel cell catalysts for the oxygen reduction reaction (ORR). A deep understanding of their atomic-scale structure, formation and degradation is a prerequisite for their use as rationally-designed NP catalysts. Here, we present results from a comprehensive microstructural study of the growth and degradation of various octahedral Pt-alloy NPs performed using ex situ, in situ and identical location high-resolution (S)TEM combined with EEL and EDX spectroscopy. We show that the NPs often show compositional anisotropy and form Ni-rich {111} facets, leading to complex structural degradation during ORR electrocatalysis. We also reveal element-specific anisotropic growth as the reason for their compositional anisotropy and limited stability. In situ thermal annealing of phase-segregated octahedral Pt-Ni alloy NPs was performed to study their morphological stability and surface compositional evolution. On being annealed, the Pt-rich surface atoms at the corners/edges diffuse onto and subsequently cover the concave Ni-rich {111} surfaces, leading to the formation of favorable flat Pt-rich {111} surfaces with Ni-rich subsurface layers. Finally, we present results from a systematic comparison of Rh-doped and undoped Pt-Ni NPs and demonstrate that surface doping of octahedral Pt-Ni NPs is found to be an effective method for stabilization of the octahedral shapes of the NPs thereby improving their long-term stability during electrochemical cycling.

N..0
14:50
Authors : Kari Laasonen*, Nico Holmberg, Rasmus Kronberg, Garold Murdachaew, Mikko Hakala, Lauri Partanen
Affiliations : Aalto University, Department of Chemistry and Materials Science

Resume : I will present an overview of density functional theory (DFT) based molecular modelling of hydrogen and oxygen evolution reactions (HER and OER). The emphasis is on the fast screening type modelling (ΔG) of various catalyst. We have studied HER on several different catalyst, including carbon nanotube (CNT) based materials [1], MoS2 [2], Ni2P [3] and Ni-oxo-hydride. In addition, the OER can be studied with ΔG-type models [4]. In all these studies the role of catalyst doping has been addressed. On MoS2 and Ni2P, the metal doping has been considered and in CNT the N doping has been studied in detailed [1,4]. Some remarks of the limitations of the ΔG models and models with explicit water molecules will be discussed. Overall, the molecular modelling of electrochemical reactions in under intense development and many new methods have been introduced recently. One of them is the use of contrained-DFT for studying coupled electron-proton transfer reaction [5]. References [1] N. Holmberg, and K. Laasonen, J. Phys. Chem. C. 119, 16166 (2015). [2] M. Hakala et al., Sci. Rep. 7, 15243 (2018), R. Kronberg et al., Phys. Chem. Chem. Phys. 19, 16231 (2017) [3] L. Partanen, and K. Laasonen, Phys. Chem. Chem. Phys., 21, 184-191, (2019). [4] G. Murdachaew and K. Laasonen, J. Phys.Chem. C, 122, 25882, (2018). [5] N. Holmberg and K. Laasonen, J. Chem. Phys. 149, 104702, (2018).

N..0
Start atSubject View AllNum.Add
09:00
Authors : F.M. Sapountzi, J.W. Niemantsverdriet
Affiliations : SynCat@DIFFER, Syngaschem BV, P.O. Box 6336, 5600 HH, Eindhoven, The Netherlands, www.syngaschem.com

Resume : Water electrolysis is an appealing solution to energy sustainability, being able to convert surplus electrical energy to chemical energy by producing hydrogen for end-use and as an energy storage medium. Among the various approaches, alkaline electrolysis is the only commercialized technology, since it relies on low-cost electrocatalysts. However, its market penetration is still low due to limited efficiency and insufficient compatibility with the intermittency of renewables. On the other hand, PEM electrolysers utilize a H conducting polymer electrolyte and have a zero-gap design which offers high currents and responsiveness to variable power input. PEM electrolysis has not yet reached commercialization because platinum-group metal (PGM) electrocatalysts are required due to the acidic nature of the membrane. To address this, research is directed towards the development of acid-stable low-cost electrocatalysts (i.e. transition metal sulfides/phosphides). An alternative approach is the replacement of the H exchange membrane with an Anion Exchange Membrane. This technology, known as AEM electrolysis, combines the merits of PEM (zero-gap design) and alkaline electrolysis (non-PGM electrocatalysts), but alkaline membranes suffer from low ionic conductivity and poor stability. In this presentation the current status, challenges and perspectives of PEM and AEM water electrolysis will be discussed in terms of the applicability of emerging materials into realistic conditions.

N..0
09:30
Authors : Bernd Oberschachtsiek, Volker Peinecke, Ivan Radev, Sebastian Stypka
Affiliations : Zentrum für BrennstoffzellenTechnik GmbH - The Hydrogen and Fuel Cell Center

Resume : Water electrolysis (WE) and fuel cells (FC) are becoming highly attractive technologies in coupling the sectors electricity supply, mobility and transport, heating, energy storage and industry in a future sustainable energy and economic system. Two different polymer electrolyte membrane technologies are currently under enhanced investigation – the more mature proton exchange membrane (PEM - acidic environment) which requires PGM catalysts and which is already used in commercial available products and the recently developed anion exchange membrane (AEM - alkaline environment) which enables non-PGM catalysts application but up to now is suffering from poor stability. Oxygen reduction reaction (ORR) in FC and oxygen evolution reaction (OER) in WE are still one of the most challenging reactions in catalysis. Although studies on new Pt and Ir alloys and Pt-free systems are promising, Pt (PEMFC) and Ir (PEMWE) are still considered as benchmark catalysts. Recently developed catalysts and catalyst layers show extremely high activity, performance and durability for both reactions in lab scale but in industrial scale devices their high potential is not yet utilized. The entire process from a lab scale synthesis and tests of active materials (membranes, ionomers, catalysts, catalyst layers, porous structures) to membrane electrode assemblies (MEA) for the use in industrial applications is highly challenging in terms of cost, duration and capital risk. ZBT has the experience and know-how to identify promising active materials for FC and WE via self-developed stepwise testing algorithms and protocols using commercial as well as self-developed test systems and can demonstrate their performance in fully functional close-to-industry operating systems with an active area of up to 400 cm^2.

N..0

Symposium organizers
1 Lifeng LIUInternational Iberian Nanotechnology Laboratory (INL)

Av. Mestre Jose Veiga, s/n 4715-330 Braga, Portugal

lifeng.liu@inl.int
2 Richard E. PALMERSwansea University

Bay Campus, Fabian Way, Swansea, SA1 8EN, U.K.

r.e.palmer@swansea.ac.uk
3. Vladimir SMIRNOVForschungszentrum Jülich GmbH

Institute for Energy and Climate Research - 5 (IEK-5), Wilhelm-Johnen-Strasse, 52425 Juelich, Germany

v.smirnov@fz-juelich.de
4. Li SONGUniversity of Science & Technology of China

National Synchrotron Radiation Lab, 42 Hezuohua Road, Hefei Anhui 230029, China

song2012@ustc.edu.cn