Influence of Vanadate Structure on Electrochemical Surface Reconstruction and OER Performance of CoV₂O₆ and Co₃V₂O₈

Underlying factors responsible for superior phase-dependent electrocatalytic OER activity of crystalline Co-vanadates are investigated. Previous reports on Co-vanadates ascribed activity differences to optimal metal–oxygen bond strength. In contrast, we found etching of vanadate from precatalyst during electrochemical activation to be the primary contributor. The resulting higher surface reconstruction exposes a higher number of catalytically active cobalt sites that otherwise lay inactive due to their position in bulk. Co-vanadates with polymeric vanadates (CoV2O6) showed better OER over monomeric orthovanadates (Co3V2O8) due to higher vanadate etching. Further, this work validates that etching can happen even from lattice positions, where bonding between constituents is strong.