Theoretical insight into the electronic and photocatalytic properties of Cu2O from a hybrid density functional theory

A comprehensive first-principle investigation, based on hybrid density functional theory, produces strong evidence that the Cu2O band-edges do satisfy the requirements of the H+/H2 and O2/H2O redox levels, demonstrating that it has enough driving force for photocatalytic overall water splitting. The calculated band gap of Cu2O 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+ to H2. The strong optical absorption of Cu2O is beneficial to overall water splitting under visible light irradiation. Possible reasons for no observation of H2 in some experiments are also discussed. The results address the ongoing controversy associated with photocatalytic overall water splitting of Cu2O.