Microwave hydrothermal synthesis of calcium antimony oxide hydroxide with high photocatalytic activity toward benzene.

A nanocrystalline CaSb2O5(OH)2 photocatalyst synthesized from CaCl2 and K2H2Sb2O7 was used to degrade benzene in the gas phase for the first time. The obtained sample was characterized by X-ray diffraction, N2 sorption-desorption, UV-vis diffuse reflectance spectroscopy, transmission electron microscopy, electron spin resonance, and X-ray photoelectron spectroscopy. The CaSb2O5(OH)2 sample had an average particle size of approximately 8 nm, a specific surface area of 101.8 m2 g(-1), and a band gap of 4.6 eV. Photocatalytic activity of the sample was mainly evaluated by the degradation of benzene in an O2 gas stream under ultraviolet light irradiation. The results demonstrated that the photoactivity of CaSb2O5(OH)2 was higher than that of commercial TiO2 (P25, Degussa Co.). In the photocatalytic degradation of benzene, it finally reached a steady conversion ratio of 29%. CaSb2O5(OH)2 has also exhibited activity toward other aromatic organic compounds. A possible mechanism of photocatalysis over CaSb2O5(OH)2 nanocrystals was proposed.