Insights into the H_2O/V_2O_5 Interface Structure for Optimizing Water-splitting

The interaction of water(H_2O) with metal oxide surfaces is of fundamental importance to various fields of science, ranging from batteries to catalysis. In particular, vanadium pentoxide(V_2O_5) has been widely used as electrode materials for aqueous-battery and catalysts. Herein, theoretical(density functional theory) study gives atomic-scale insights into water monolayers in V_2O_5 and single-molecule adsorption and dissociation at three low-index surfaces and oxygen-vacancy V_2O_5(001) surface. The H_2O/V_2O_5 interface structure was identified. The results show that H_2O is adsorbed on the stoichiometric V_2O_5(001) surface with physisorption mechanism, and the dissociation hardly occurs. Water adsorbs as an intact monomer with a computed binding energy of 0.75 eV. The formation of ordered water overlayers has been observed on V_2O_5(001) surface, suggesting a locally ordered superstructure of molecular water. The molecular H_2O adsorption on oxygen-vacancy V_2O_5(001) surface is stronger than that on the stoichiometric V_2O_5(001) surface, and H_2O can undergo dissociative chemisorption to form a surface hydroxyl group and a H adatom. V_2O_5 can take the oxygen from H_2O, which is consistent with the experimental results.