First-principles study of properties nonmetals(C,N,S,P) doped anatase TiO₂

Abstract

Anatase TiO2 semiconductor cell and TiO1.875X0.125(2×1×1) (X is C, N, S, P) with the replacement of O with C, N, S, P atom were produced by Materials studio software.Energy band structure, density of state(DOS) and optical properties were analysed by Castep software package based on density functional theory(DFT).The results showed that nonmetal doping led to the width of gap decreased to 0.57 eV(TiO1.875C0.125), 1.93 eV(TiO1.875N0.125), 1.30 eV(TiO1.875S0.125) and 0.21 eV(TiO1.875P0.125) and their adsoption band edge had different degree of red shifts toward the long wavelength(TiO1.875P0.125> T iO1.875C0.125> TiO1.875S0.125> TiO1.875N0.125).Nonmetal doping narrowed the band gap width and made the energy band denser.Valence band and condiction band of C and P doping both moved to the low energy area, in addition, the conduction band of N and S doping moved to the low energy area but valence band hardly moved.Different numbers of impurity energy levels were generated in different state of band gap due to the hybridization and coupling between C-2p, N-2p, S-2p, P-3p, O-2p and Ti-3d.The impurity energy levels generated new visible-light adsoption areas, catching electrons from valence band and inhibiting electronic/hole combination, which enhanced the photocatalytic activity.Above all, C, P doped anatase TiO2 have narrower band width, narrower band gap, wider redshift and higher photocatalytic activity under visible-light.

Keywords

• nonmetal doping
• anatase tio₂
• first-principles
• band structure
• density of state