Speakers and Abstracts

Avner Rothschild is a professor at the Department of Materials Science and Engineering of the Technion. He studied physics and materials engineering at the Technion – Israel Institute of Technology, and graduated in 2003 with a PhD on metal-oxide gas sensors. After a three-year postdoc at MIT he returned to the Technion as a faculty member at the Department of Materials Science and Engineering, and the head of the Electrochemical Materials & Devices research group. His research focuses on electrochemical and photoelectrochemical materials and devices for water splitting as a means of sustainable production of green hydrogen from renewable energies such as solar and wind.
Professor Rothschild is a co-founder of H2Pro, a startup company that develops a transformative water splitting technology for low-cost production of green hydrogen at scale. He was a member of several European consortia and had an ERC consolidator grant on photoelectrochemical water splitting. He is a fellow of the Royal Society of Chemistry, and in 2020 he won the 2020 Eric and Sheila Samson Prime Minister's Prize for Global Innovation in Alternative Fuels for Transportation.

Wasted Photons: Photogeneration Yield and Charge Carrier Collection Efficiency of Metal Oxide Photoanodes for Photoelectrochemical Water Splitting

At the heart of solar cells is a semiconductor photoabsorber: a material capable of absorbing photons and generating electrons and holes that contribute to the photocurrent. But where commercial photovoltaic cells use silicon for that purpose, photoelectrochemical water splitting cells for solar energy conversion to green hydrogen must rely on other materials that are suitable for operation in aqueous electrolytes. Selected transition metal oxides such as TiO2 and -Fe2O3 (hematite) are known for their stability in alkaline electrolytes, which makes them prime candidates for photoanodes for water photo-oxidation. While transition metal oxides with empty d-shell configurations such as TiO2 (Ti4+ 3d0) and BiVO4 (V5+ 3d0) reach high internal quantum efficiencies, their lower bandgap counterparts with open d-shell configurations such as hematite (Fe3+ 3d5) display low quantum efficiencies that limit their photoconversion efficiency. In the case of hematite photoanodes, less than half of the theoretical photocurrent limit has been reached, despite half a century of research efforts to improve their performance.
Nearly all of these efforts address electron-hole recombination losses in the bulk and at the surface by nanostructuring and co-catalysis, respectively, whereas only few studies have considered the deleterious effect of localized d-d transitions that do not generate electrons and holes. Here we present an analytical way of assessing the actual limit that might be obtained from hematite, as a case-study for other correlated electron materials. To this end, a comprehensive method is introduced to extract both the spatial profile of the charge carrier collection efficiency and the photogeneration yield spectrum, defined as the wavelength-dependent fraction of absorbed photons that generate electron–hole pairs. Our results show  that photogeneration yield in thin film hematite photoanodes is less than unity across the entire absorption range, limiting the maximal photocurrent that may be attained in an ideal hematite photoanode to about half of the theoretical limit predicted without accounting for this effect. Our method is applicable to other materials, and we hope that this study will inspire further research into the effect of noncontributing light absorption in photocatalytic materials with correlated electrons that often give rise to nontrivial physical phenomena that may affect their properties and performance.

Institut für Physik, Karl-Franzens Universität Graz, AT

Martin Sterrer is the head of the Surface Physics Group at the Institute of Physics at the University of Graz. He obtained his PhD in Physical Chemsitry at Vienna University of Technology under the supervision of Prof. Erich Knözinger. From 2003 to 2006, he worked at the Fritz Haber Institute of the Max Planck Society in Germany as a Postdoctoral fellow with Prof. Hajo Freund. After a stint at the FOM Institute for Atomic and Molecular Physics in Amsterdam in the Biosurface spectroscopy group of Prof. Mischa Bonn, he went back to the Fritz Haber Institute and became the leader of the working group Catalysis/Laser spectroscopy. From 2008 to 2010, Sterrer was a lecturer at the Technische Universität Berlin, where ce received his Habilitation in 2013. He joined the University of Graz as Professor of Experimental Physics in 2014.
His research fields include model catalysis on oxide-supported metal nanoparticles, the investigation of processes at solid-liquid interfaces, and adsorption studies on metal and oxide surfaces, using methods such as scanning tunnelling microscopy, photoemission spectroscopy and vibrational spectroscopy.

Charge Transfer at Metal/Oxide/Organic Interfaces

Charge transfer processes through ultrathin, supported oxide films have received increasing attention in recent years because of the possibility to control the charge state of adsorbates or the direction of catalytic reactions. The main driving force for the occurrence of charge transfer in these systems is the reduction of the substrate work function induced by deposition of the oxide film in combination with an adsorbate with high electron affinity. While previous studies have focused on the charging of metal atoms (e.g. Au) or small molecules (e.g. O2, NO2), we have recently extended these investigations to charge transfer processes into organic molecules. In this contribution, we present results on the adsorption and charging of model organic semiconductors (e.g. pentacene (5A), 2H-tetraphenylporphyrin (2H-TPP) and others) on ultrathin MgO(001) films supported on Ag(001). By combing scanning tunneling microscopy and photoemission spectroscopy and tomography, we identify and quantify charge transfer into the organic monolayer film. In addition, we show that by variation of the work function and the MgO thickness it is possible to drive the system into a state where no charge transfer occurs. In the case of 2H-TPP, charge transfer also appears to strongly influence the self-metalation of 2H-TPP to Mg-TPP. Thus, our investigations lay the basis for the ultimate control of charge transfer, and the related chemistry, on ultrathin oxide film systems.

Neutron Sciences, Oak Ridge National Laboratory, USA

Timmy Ramirez-Cuesta is the leader of the Chemical Spectroscopy Group at the Oak Ridge National Laboratory. He studied physics in Argentina and completed his PhD Thesis working on computer modeling of chemical reaction on surfaces. He worked at the Rutherford Appleton Laboratory in the UK as a senior instrument scientist at the TOSCA spectrometer. He developed the methodology to calculate the results of dynamical properties calculations. Ramirez-Cuesta is the author of the ICEMAN software and the coauthor of the book Vibrational Spectroscopy with Neutrons: with applications in Chemistry, Materials Science and Catalysis; World Scientific 2005. He joined ORNL in 2013.
His research interests include Vibrational Spectroscopy, Inelastic Neutron Scattering Spectroscopy, computer modeling, characterization of hydrogen storage systems, metal hydrides, and porous materials, catalysis, etc.

Inelastic Neutron Scattering in Chemistry and Catalysis

A wide range of advanced experimental methods has been used in catalytic science to understand molecular behavior in chemical processes. Neutron scattering gives information that is highly complementary from other microscopic scattering techniques such as electrons (microscopy and diffraction) photons from visible light to synchrotron X-rays standard laboratory measurement.
With catalysis experiments, it is often necessary to load gases and control the reaction temperature and pressure. The development of sample environment is therefore essential. One thing we can take advantage of is the high penetration of neutrons, which means we can choose from a lot more materials, including the very hard ones such as steel or copper-beryllium.
A general overview of inelastic neutron scattering and some application in catalysis will be presented. 

Jenny Zhang completed her PhD in bioinorganic chemistry at the University of Sydney, then became a Marie Curie Incoming International Fellow at the University of Cambridge to explore how biocatalysts can be exploited to generate solar fuels. In particular, she worked on developing strategies to re-wire oxidoreductases, such as the water-oxidation enzyme photosystem II, to electrodes/semiconductors/other proteins in an emerging field known as 'semi-artificial photosynthesis'.
She has since been awarded a BBSRC David Phillips Fellowship at the Yusuf Hamied Department of Chemistry, where she has started her own research group. Here, she takes on the re-wiring of photosynthesis to another level of complexity - in live cells and using 3D printing! She has recently been awarded the RSC Felix Franks Biotechnology Medal for her research work.

Photosynthesis on an Electrode

Photosynthesis is the primary route from which solar energy is harnessed to fuel life on Earth. Underlying this important process are impressive machineries that convert Earth-abundant resources (sunlight, water and carbon dioxide) into complex chemicals. We now have the capability to electrochemically tap into the photosynthetic electron transport chain in vivo and harness its electrons for alternative energy conversion technologies [1, 2]. However, enormous hurdles remain when wiring photosynthetic components to electrodes compared to the wiring of molecular catalysts or enzymes. [3]
Here, I will talk about how photosynthesis can be wired to electrodes – from purified proteins to living whole cells; what we can gain from doing this; and what are the future possibilities using this approach.