First-principles study of the electronic and optical properties of the (Eu,N)-codoped anatase TiO2 photocatalyst

► There are some impurity states (N2p,Eu4f) appearing in the band gap for doping TiO2 systems. ► The band gap of (Eu,N)-codoped anatase TiO2 has an obvious decline. ► The synergistic effects of codoping TiO2 induces red-shift of optical absorption edge. ► Photocatalytic activity of (Eu,N)-codoped TiO2 were firstly explained with DFT calculation.