Understanding electronic and optical properties of N-Sn codoped anatase TiO2

Understanding photoelectrochemical properties of N-Sn codoped anatase TiO2 is attractive and significant for their potential applications in solar photocatalysis. In this work, we use density functional theory plus U (DFT + U) calculations to investigate the electronic structures and optical properties of Sn-, (N, Sn), and (2N, Sn) doped anatase TiO2. It is found that Sn monodoping, (N, Sn) codoping and even (2N, Sn) codoping by two non-adjacent N atoms cannot lead to an effective band gap narrowing. In contrast, (2N, Sn) codoping by two adjacent N atoms can result in a much more effective band gap narrowing, due to the appearance of the effective N-N coupling that can form two distinguishable occupied states in the forbidden gap. Our results show that the coupling between N atoms plays a key role in the enhanced visible light photocatalytic activity of N-Sn codoped anatase TiO2. (C) 2014 Elsevier B.V. All rights reserved.