Screening Transition-Metal-Incorporated β-AgVO for Augmented Oxygen Reduction Activity.

Exploring cost-effective alternatives to Pt-based catalysts for the oxygen reduction reaction (ORR) in fuel cells is crucial for their large-scale deployment in green energy applications. Silver vanadate (AgVO) is a well-studied material for photocatalytic applications. Here, we investigate the electrocatalytic ORR activity of the thermodynamically stable β phase of AgVO through computational modeling based on DFT. It is found that β-AgVO exhibits weak catalytic activity for the ORR, with vanadium being the preferable active site. Incorporating single atoms of transition metals at surface-level vacancies in β-AgVO significantly modifies the ORR activity. We study the scaling of free energy changes for the ORR intermediates *OOH, *OH, and *O for various transition metals incorporated, which leads to an optimal overpotential for the system. The optimal overpotential thus obtained is remarkably lower than that of pristine β-AgVO. For the transition metal atoms we consider here, Co-incorporated β-AgVO exhibits the best ORR catalytic activity due to its optimal binding of ORR species to the vanadium site. It is also observed that some of the transition metals considered like Re, Rh, Os, or Mn show weak activity, either due to strong or weak binding. Analysis of the electronic structure of the adsorbate-catalyst interface shows a strong correlation between optimal activity and evolution of midgap states in β-AgVO, due to transition metal incorporation. Our study concludes that the ORR activity of a stable mixed transition metal oxide like β-AgVO can be enhanced with a minimal loading of transition metals, which could help in developing a novel series of ORR catalysts.