Facile Synthesis of N‐doped TiO₂ and Its Enhanced Photocatalytic Activity for Degrading Colorless Pollutants

N‐doped nanocrystalline TiO 2 is synthesized successfully through a simple ammonia‐modified hydrolysis‐solvothermal process. It is demonstrated that the resulting TiO 2 doped with an appropriate amount of N exhibits high visible photocatalytic activities for the degradation of gas‐phase acetaldehyde and liquid‐phase phenol, which is attributed to its increased visible adsorption, appropriate crystallinity, and good dispersibility, whereas its UV activity is decreased. On the basis of the atmosphere‐controlled surface photovoltage spectra, it is found that the doped N species can capture the photogenerated holes so as to be favorable for photogenerated charge separation, so it is suggested that its decreased UV activity results from its weak adsorption of O 2 compared with that of undoped TiO 2 , as shown by the O 2 temperature‐programed desorption curves. Interestingly, the photocatalytic activity of the resulting N‐doped TiO 2 under visible or UV irradiation can be improved further by promoting O 2 adsorption after modification with an appropriate amount of phosphoric acid.