This work focused on improving the photocatalytic activity of N-doped TiO2 photocatalyst for efficiently utilizing solar energy. A simple H2 reduction was found to remarkably enhance the photocatalytic activity of N-doped TiO2 for ethylene oxidation under visible light or simulated solar light irradiation. Ultraviolet/visible diffuse reflectance spectra (UV/vis DRS), X-ray photoelectron spectra (XPS) and electron paramagnetic resonance (EPR) spectra were employed to characterize the surface properties and chemical states of nitrogen dopants in H2-reduced N-doped TiO2. The results revealed that H2 reduction facilitated the creation of oxygen vacancies and Ti3+ species in N-doped TiO2 but without removal of nitrogen species from catalyst surfaces. The formed oxygen vacancies and Ti3+ species seriously influence electron excitation from doped nitrogen species and subsequently tune the generation of active oxygen species O2•− radicals on N-doped TiO2. The synergistic effect of oxygen vacancies and doped nitrogen species contributes to the enhancement of photocatalytic activity of N-doped TiO2 samples, but the formed Ti3+ ions largely suppress the photocatalytic activity.

Controlling the Synergistic Effect of Oxygen Vacancies and N Dopants to Enhance Photocatalytic Activity of N-Doped TiO2 by H2 Reduction. Zhang, Z., Long, J., Xie, X., Zhuang, H., Zhou, Y., Lin, H., Yuan, R., Dai, W., Ding, Z., Wang, X., Fu, X.: Applied Catalysis A, 2012, 425–426, 117–24