Shaping the energy landscape toward renewable energy resources is a contemporary challenge that requires significant advancements in the development of catalysts for energy conversion and storage via fuel cells, electrolyzers, and metal-air batteries. We focus on engineering complex, nonstoichiometric mixed metal oxides as a potential avenue for generating robust heterogenous electrocatalysts for electrochemical transformations related to energy and chemical conversion and addressing the limitations with the current state-of-the-art supported metal based electrocatalysts. The compositional versatility of nonstoichiometric metal oxides of the general form An+1BnO3n+1 (where n = 1 (Ruddlesden-Popper layered structure) to ∞ (perovskite structure); A = rare earth/alkaline earth metal cation; B = transition metal cation) presents numerous opportunities to tune the catalytic performance of these oxides for targeted reactions. While promising, identification of robust nonstoichiometric metal oxides for these reactions is often limited by their complexity and lack of effective descriptors of their activity and stability. We have combined controlled synthesis, advanced characterization, electro-kinetic studies and theory to shed light on the factors that govern the energetics of key electrochemical reactions, including electrochemical reduction and evolution of oxygen (ORR/OER) and electrochemical reduction of CO2 to CO, on nonstoichiometric mixed metal oxides. The aim has been to use these insights to identify ways to tune the activity, selectivity and stability of these oxides. We have specifically shown that (i) the electronic structure of the transition metal cations in these oxides can be systematically tuned via oxide compositional variations to achieve the outmost reactivity for targeted electrochemical reactions, and (ii) the oxide framework can act as a platform for in situ generation of highly catalytically active surfaces under electrochemical conditions. These advances have paved the way for engineering active, selective and stable catalytic cationic sites in nonstoichiometric mixed metal oxides for electrochemical reactions with relevance to energy conversion and storage.

Embracing the complexity of heterogeneous catalytic structures: Electrocatalysis by nonstoichiometric mixed metal oxides

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.