Mechanistic study of N-H- and H-N-codoping of a TiO₂ photocatalyst for efficient degradation of benzene under visible...

Non-metal codoping including nitrogen (N) and hydrogen (H) codoping has been emerging as an effective way to improve the performance of anatase TiO₂ in solar cell, fuel conversion and pollutant degradation. However, the mechanism of the synergistic effect of N doping and H doping on TiO₂ is still far from thorough. In this paper, N and H codoped TiO₂ 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-TiO₂ photocatalyst was fully elaborated by comparing with H-N-TiO₂, which was obtained by thermal treating in H₂ and then NH₃. The reaction rate of N-H-TiO₂ in the photocatalytic degradation of benzene was nearly 2 times that of H-N-TiO₂, ∼7 times higher than that of pristine TiO₂. Furthermore, the cycling test revealed the high repeatability and stability of the N-H-TiO₂ photocatalyst. The excellent performance N-H-TiO₂ was attributed to an adequate concentration of N_iH_i defects occupying interstitial sites of the TiO₂ structure and a disordered surface layer introduced by annealing in NH₃ and H₂ 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 TiO₂.