C/B codoping effect on band gap narrowing and optical performance of TiO2 photocatalyst: a spin-polarized DFT study

Abstract

The electronic and optical properties of several possible C/B-codoped models of anatase and rutile TiO₂ have been investigated systematically using spin-polarized density functional theory calculations. Our calculated results show that the synergistic effect of C/B codoping can induce some hybridized energy states appearing in the forbidden gap and the band gap has a narrowing in anatase and rutile TiO₂, which can lead to a decrease of the photon excitation energy and an obvious red-shift of the optical absorption edge. These results lead to an excellent photocatalytic activity in C/B-codoped TiO₂. Moreover, with the increase of C and B impurities’ concentration in anatase and rutile TiO₂, we find that the intensity of impurity states has a strengthening in the band gap, the position of impurity states changes, and the visible-light absorption performance improves gradually.