Mechanistic study of N-H- and H-N-codoping of a TiO photocatalyst for efficient degradation of benzene under visible light.

Non-metal codoping including nitrogen (N) and hydrogen (H) codoping has been emerging as an effective way to improve the performance of anatase TiO in solar cell, fuel conversion and pollutant degradation. However, the mechanism of the synergistic effect of N doping and H doping on TiO is still far from thorough. In this paper, N and H codoped TiO nanoparticles are obtained by N doping in ammonia and then H doping in hydrogen gas, which achieves substantially boosted efficiency and reaction rate in the photocatalytic degradation of benzene under visible light excitation. The superiority of the N-H-TiO photocatalyst was fully elaborated by comparing with H-N-TiO, which was obtained by thermal treating in H and then NH. The reaction rate of N-H-TiO in the photocatalytic degradation of benzene was nearly 2 times that of H-N-TiO, ∼7 times higher than that of pristine TiO. Furthermore, the cycling test revealed the high repeatability and stability of the N-H-TiO photocatalyst. The excellent performance N-H-TiO was attributed to an adequate concentration of NH defects occupying interstitial sites of the TiO structure and a disordered surface layer introduced by annealing in NH and H successively. The synergistic effect of N-H-codoping also increased the separation and migration of electron-hole pairs triggering a photoinduced redox reaction on the surface of TiO.