Roles of Cu concentration in the photocatalytic activities of Cu-doped TiO2 from GGA+U calculations

•3d Electrons in Ti and Cu are correctly described.•Influence of Cu concentration on photocatalytic activity of TiO2 are first reported.•Cu-induced gap states result in band gap narrowing of host TiO2.

First-principles GGA+U calculations are performed on the electronic structure of Cu-doped anatase TiO2 with various Cu concentrations. The results show that the incorporation of Cu into TiO2 gives rise to a perturbation of electronic structure. The most remarkable feature is the appearance of metal-induced gap states, resulting in the band gap narrowing of host TiO2. The band gaps reduce with the increase of Cu concentration. Both the positions of valence band maximum and conduction band minimum depend on Cu concentration, which indicates that there should be an optimal Cu concentration to achieve high H2 generation efficiency.