Theoretical insight into the electronic and photocatalytic properties of Cu sub(2)O from a hybrid density functional theory

A comprehensive first-principle investigation, based on hybrid density functional theory, produces strong evidence that the Cu sub(2)O band-edges do satisfy the requirements of the H super(+)/H sub(2) and O sub(2)/H sub(2)O redox levels, demonstrating that it has enough driving force for photocatalytic overall water splitting. The calculated band gap of Cu sub(2)O is 2.184 eV, which is consistent with the experimental value of 2.17 eV. The highly dispersive s-s hybrid states at the conduction band bottom result in a small effective mass of the electron, which is favorable to carrier separation and the carrier transfer to surface, and thus facilitate the reduction of H super(+) to H sub(2). The strong optical absorption of Cu sub(2)O is beneficial to overall water splitting under visible light irradiation. Possible reasons for no observation of H sub(2) in some experiments are also discussed. The results address the ongoing controversy associated with photocatalytic overall water splitting of Cu sub(2)O.