Synthesis of Efficient Nanosized Rutile TiO2 and Its Main Factors Determining Its Photodegradation Activity: Roles of Residual Chloride and Adsorbed Oxygen

Nanosized TiO2 containing different contents of rutile phase was controllably synthesized by a hydrochloric acid-modified hydrothermal process. It is demonstrated that the formation of rutile phase in TiO2 mainly depends on the role of chlorine anions in the synthesis, and a certain amount of residual chloride would exist on the surfaces of the resulting nanocrystalline rutile TiO2. Interestingly, the as-prepared rutile shows high activity for photodegradation of rhodamine B dye compared with the as-prepared anatase, even superior to the P25 TiO2. It is mainly attributed to the residual chloride that could promote the dye adsorbed on the surfaces of TiO2, consequently accelerating the photosensitization oxidation reactions of the dye molecules. In the photodegradation of liquid-phase phenol and gas-phase aldehyde, the as-prepared rutile TiO2 samples display low activity, which is attributed to the photogenerated electrons weakly captured by the adsorbed oxygen, since the residual chloride could effectively capture photoinduced holes based on the atmosphere-controlled surface photovoltage spectroscopy results. Further, the photoactivity of resulting rutile for degrading phenol and aldehyde is greatly enhanced by modifying a proper amount of phosphoric acids to increase the adsorption of O-2, even higher than that of the P25 TiO2. This work would explore feasible routes to synthesize efficient nanosized rutile TiO2-based photocatalysts for degrading colored and colorless organic pollutants by investigating the rate-determining factors in the photodegradation processes.