First-principles calculation of N:H codoping effect on energy gap narrowing of Ti O 2

The energy band structures and density of states for N-doped and N:H-doped anatase Ti O 2 are calculated based on the first-principles density-functional theory. For N-doped Ti O 2 , there appear two isolated states above the top of the valence band and the band gap narrowing is very small. With the same nitrogen dopant concentration, N:H doping yields a significant band gap narrowing. The calculated results support our experimental data that N:H-doped Ti O 2 exhibited higher visible-light photocatalytic efficiency than the N-doped one.