Improved photocatalytic activity of rutile TiO2 for organic oxidation through Ag nanoparticles and borate anions

Abstract

Rutile TiO2 (RT) is usually used as photocatalyst for water oxidation, but seldom for organic oxidation, probably due to the slow reduction of O2. Herein we report a mutual effect of Ag nanoparticles and borate anions greatly increasing the photocatalytic activity of RT for phenol oxidation in neutral aqueous solution. RT was home-made, followed by calcination at 200―800 °C. With a given RT, the rates of phenol oxidation on the addition of Ag and borate were increased and decreased, respectively. In the presence of both Ag and borate, interestingly, the rate of phenol oxidation was larger than that in the presence of Ag. A (photo)electrochemical measurement revealed that Ag and borate, in contact with the irradiated RT, could catalyze O2 reduction and phenol oxidation, respectively. Since the electron and hole transfer processes would promote each other, the positive effect of Ag is further enhanced in the presence of borate. This work demonstrates that RT could be developed as a promising photocatalyst for organic oxidation through a surface co-catalyst.