Design Strategies for Efficient Nonstoichiometric Mixed Metal Oxide Electrocatalysts: Correlating Measurable Oxide Properties to Electrocatalytic Performance

Recent advances in the use of nonstoichiometric mixed metal oxides belonging to the perovskite family as cost-effective catalysts for various oxygen-related heterogeneous thermochemical and electrochemical reactions have led to the need for the development of robust design criteria to tune their catalytic performance. The current paradigm for describing the electrocatalytic activity of these oxides relies on the averaged oxidation state of the transition metal in the structure, which often fails to systematically describe activity. In addition, the current design strategies mainly focus on activity and often overlook oxide stability. Therefore, the development of robust criteria that rely on measurable oxide properties and can shed light on the electrochemical activity and stability of these oxides still remains a challenge. Herein, we demonstrate an approach for correlating experimentally measurable oxide properties (i.e., oxide surface reducibility) with the oxide activity and stability. This is demonstrated through the use of electrochemical oxygen reduction reaction (ORR) as a probe reaction. We show that the oxide surface reducibility describes the transition metal-lattice oxygen bond strength and captures effects from both the oxide composition and crystal symmetry on the binding energetics of the oxygenated intermediates and consequently the ORR activity and stability. Comprehensive design strategies for efficient ORR. on nonstoichiometric mixed metal oxides are devised. Such strategies have the potential to be extended to other oxygen-related catalytic reactions on these nonstoichiometric mixed metal oxides.