(678a) How Metal/Support Heterostructures Influence the Design Principles and Limiting Potentials for the Oxygen Reduction Reaction

Platinum-based catalysts are widely used for the Oxygen Reduction Reaction (ORR) in fuel cells, metal-air batteries, and electrolyzers due to their excellent electrocatalytic activity and stability. However, platinum's high cost and scarcity has led to extensive research efforts in alloying platinum with other transition metals, modifying its surface properties, and utilizing its nanostructures. Experimentally synthesizable, rationally designed supported metal films on various earth-abundant carbides and nitrides may also have the potential to attain the theoretical maximum for ORR and achieve high activity and stability with low Pt usage.

In this study, we selected nonmagnetic 2D and 3D metal carbides and nitrides (TiC, TiN, VC, VN, CrN, NiC, NiN, MoC, MoN, and WC) with their (111) facets exposed, and adsorbed mono- and bilayers of Pt, Ag, and Au epitaxially and non-epitaxially. We assessed the thermodynamic and electrochemical stability of the films and evaluated their ORR catalytic activity using the computational hydrogen electrode framework by explicitly calculating the limiting potentials. The OOH* vs OH* scaling relation deviates from the bond order conservation slope of 1 (seen across unsupported metals, alloys, and single-atom catalysts). This deviation in slope results in the ORR volcano peak shifting upward by 0.15 V, relative to the unsupported metal catalysts. This is because the metal film's reactivity is modulated by electronic metal-support interaction (EMSI) as well as strain. We identify at least 10 heterostructures with higher limiting potentials than Pt (111), including Pt/CrC with the highest at 0.93 V. We perform a detailed electronic analysis on these heterostructures to predict the key features contributing to the increased activity. Tuning the reactivity of the metal film via its interaction with the underlying support opens a wide material space for the design of high-performance ORR catalysts with reduced precious metal loading.