In designing catalysts for clean energy- is the nature of the active site always the right question to ask?
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Abstract:
One of the greatest challenges of the 21st century will be securing cheap and renewable sources of energy. One of the most promising approaches to this challenge is to design catalysts from earth-abundant materials capable of implementing key chemical reactions, including splitting water into hydrogen and oxygen (H2O → 2H+ + O2); and both the oxidation (H2→ 2H+) and reduction (2H+→ H2) of hydrogen among many others. In studying catalysts, we often focus on the “nature of the active site” which for classical heterogeneous catalysts works well- but not all catalysts work by a surface sorption process alone. In some systems, it is increasingly realised that processes of precipitation and reformation may actually be key to catalysis. In this talk we explore the relationship between redox chemistry and catalytic chemistry using birnessite-like manganese oxides and iron sulfides as examples. We argue that structural disorder plays an overlooked role in some catalysts, as it alters thermodynamic stability affecting stability, electron transfer and product selectivity. The redox events between substrate and catalyst and the speed of these processes appear to play a key role in both engineering product selectivity and catalyst stability. We examine how the events after catalysis may be key for understanding the active events of catalysis as well as mechanisms of decomposition.
References:
Characterization of Energy Materials with X-ray Absorption Spectroscopy- Advantages, Challenges and Opportunities B. V. Kerr, R. K. Hocking et al Energy and Fuels 2022, 36(5) 1258-2389
Redox properties of iron sulfides: direct versus catalytic reduction and implications for catalyst design C. F. Garibello, R. K. Hocking et al ChemCatChem 2022 https://doi.org/10.1002/cctc.202200270
Speaker Biography:
Rosalie Hocking is a chemist whose research is aimed at among other things the development of new ways to understand and characterise materials– she works on electrochemical devices to make commodity chemicals (like hydrogen and ammonia) from solar-derived electricity. Where her work makes extensive use of the Australian Synchrotron where she uses X-rays to find out how new materials work, and why sometimes they don’t! She is also researching the development cheap sensor devices that would enable everyday people with materials characterisation tools important for applications like Asbestos identification on building sites. Rosalie has served as Chair of the User Advisory committee of the Australian Synchrotron and on the Program Advisory Committees for two beamlines. She also currently Deputy Department Chair of Chemistry and Biotechnology at Swinburne University of Technology.