Electronic and optical performances of (Cu, N) codoped TiO₂/g-C₃N₄ heterostructure photocatalyst: A spin-polarized DFT + U study

The geometrical, electronic and optical properties of Cu or/and N (co)doped TiO₂/g-C₃N₄ heterostructure systems have been investigated systematically on the basis of spin-polarized density functional theory calculations. Our calculated results indicate that the band gap of TiO₂/g-C₃N₄ heterostructure has an obvious narrowing compared with pure TiO₂ (1 0 1) surface, and (Cu, N) codoping can induce some impurity states of N 2p and hybridized states of Cu 3d and N 2p appearing in the forbidden gap of TiO₂/g-C₃N₄ heterostructure, which lead to a decrease of the photon excitation energy and an obvious redshift of the optical absorption edge. Moreover, the charge density difference calculations of Cu or/and N (co)doped TiO₂/g-C₃N₄ heterostructure systems show that the excited electrons and holes will eventually accumulate in (co)doping TiO₂ (1 0 1) surface and g-C₃N₄ monolayer, respectively, which can effectively reduce the recombination of the photogenerated electron-hole pairs by the interfacial coupling of between TiO₂ (1 0 1) surface and g-C₃N₄ monolayer. This work not only investigates systematically the electronic and optical properties of Cu or/and N (co)doped TiO₂/g-C₃N₄ heterostructure, but also suggests that (Cu, N) codoped TiO₂/g-C₃N₄ heterostructure is a preferable visible-light photocatalyst.