Efficient overall water-splitting enabled by tunable electronic states of vanadium-substituted P–Co3O4

Abstract

Despite the fact that phosphorus (P) partly substituted Co3O4 (P–Co3O4) has been considered as an intriguing electrocatalyst toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), the modulation of electronic property using hetero atoms to improve activities of P-rich Co3O4 catalyst remains an elusive goal. Herein, we demonstrate that the vanadium (V) doping provides the most promising strategy to significantly regulate the electronic states of P–Co3O4, thus yielding an outstanding overall water-splitting performance. A small cell voltage of 1.594 V is required to deliver the current density of 10 mA/cm2, largely outperforming the RuO2||Pt/C catalyst. It is further revealed that the added V5+ with empty 3d orbital can act as electron acceptors, which weakens the coordination of Co–O band. As a result, the electrons are inclined to transfer to the V through the O ligand, rather than to Co. We then report that the V doping could modulate the local electronic configuration and atomic arrangement of bonded Co and adjacent O atoms to enhance the electrons’ delocalization capacity of Co atoms for high electrical conductivity, as well as effectively accelerate the formation of key H∗ intermediates toward fast HER kinetics. These findings represent a new strategy for regulating the electronic properties of catalysts and are expected to open new opportunities for the development of high-performance catalysts.