Hierarchical N- Doped TiO2 Microspheres with Exposed (001) Facets for Enhanced Visible Light Catalysis

Hierarchical N-doped TiO2 microspheres with exposed (001) facets [N-TiO2-(001)] were synthesized through a simple, fluorine-free solvothermal reaction with subsequent thermal treatment. The results show that the hierarchical N-TiO2-(001) microspheres are made up of numerous TiO2 nanosheets, and that isopropylamine (IPAN) acts as both the nitrogen source and the capping and shape-controlling agent that generates the high-energy (001) facets. In addition, IPAN is also effective in increasing the onset temperature of the phase transformation of TiO2 from anatase to rutile. Compared with the commercially available P25 TiO2, the as-prepared TiO2 microspheres exhibit good photocatalytic activity and high stability under visible-light irradiation. The high photocatalytic performance is derived from the synergy effect of N-doping and the separation of photogenerated electrons and holes among different facets, as evidenced by surface photovoltage spectroscopy.