Cooperative Effects Drive Water Oxidation Catalysis in Cobalt Electrocatalysts through the Destabilization of Intermediates
Journal Article
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· Journal of the American Chemical Society
- Imperial College, London (United Kingdom); SLAC
- University of Copenhagen (Denmark)
- Institut Català d’Investigació Química (ICIQ), Tarragona, (Spain)
- Imperial College, London (United Kingdom)
- Imperial College, London (United Kingdom); University of Southern California, Los Angeles, CA (United States)
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- University of Southern California, Los Angeles, CA (United States)
- Harwell Science and Innovation Campus, Didcot (United Kingdom). Diamond Light Source
- Institut Català d’Investigació Química (ICIQ), Tarragona, (Spain); Catalan Institution for Research and Advanced Studies (ICREA), Barcelona (Spain)
A barrier to understanding the factors driving catalysis in the oxygen evolution reaction (OER) is understanding multiple over- lapping redox transitions in the OER catalysts. The complexity of these transitions obscure the relationship between the coverage of adsorbates and OER kinetics, leading to an experimental challenge in measuring activity descriptors, such as binding energies, as well as adsorbate interactions, which may destabilize intermediates and modulate their binding energies. Herein, we utilize a newly designed optical spectroelectrochemistry system to measure these phenomena in order to contrast the behavior of two electrocatalysts, cobalt oxyhydroxide (CoOOH) and cobalt-iron hexacyanoferrate (cobalt-iron Prussian blue, CoFe-PB). Three distinct optical spectra are observed in each catalyst, corresponding to three separate redox transitions, the last of which we show to be active for the OER using time-resolved spectroscopy and electrochemical mass spectroscopy. By combining predictions from density functional theory with parameters obtained from electroadsorption isotherms, we demonstrate that a destabilization of catalytic intermediates occurs with increasing coverage. In CoOOH, a strong (~0.34 eV/ monolayer) destabilization of a strongly bound catalytic intermediate is observed, leading to a potential offset between the accumulation of the intermediate and measurable O2 evolution. We contrast these data to CoFe-PB, where catalytic intermediate generation and O2 evolution onset coincide due to weaker binding and destabilization (~0.19 eV/monolayer). By considering a correlation between activation energy and binding strength, we suggest that such adsorbate driven destabilization may account for a significant fraction of the observed OER catalytic activity in both materials. Finally, we disentangle the effects of adsorbate interactions on state coverages and kinetics to show how adsorbate interactions determine the observed Tafel slopes. Crucially, the case of CoFe-PB shows that, even where interactions are weaker, adsorption remains non-Nernstian, which strongly influences the observed Tafel slope.
- Research Organization:
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Sponsoring Organization:
- British Association of Spectroscopists and Schmidt Futures; Danish National Research Foundation Centre; Engineering and Physical Sciences Research Council (EPSRC); European Union’s Horizon 2020; Generalitat de Catalunya; Spanish Ministerio de Ciencia e Innovación; USDOE Office of Science (SC)
- Grant/Contract Number:
- AC02-76SF00515
- OSTI ID:
- 2335803
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 13 Vol. 146; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English