Kinetics of the reduction reaction of selenate ions by TiO2 photocatalyst

The reduction reaction of selenate ions in an aqueous solution by TiO2 phot ocatalyst is investigated. The conduction band of TiO2 is much more positiv e than the standard redox potential of the reduction reaction of selenium t o selenide. However, the selenate ions are reduced to hydrogen selenide via amorphous selenium, by the TiO2 photocatalyst. After all selenate ions and selenite ions are reduced to amorphous selenium, no chemicals in the solut ion can capture the electrons from the TiO2 photocatalyst. Under this condi tion, photogenerated electrons accumulate in the TiO2 particles, and they r aise the conduction band of the TiO2. All the experimental results can be e xplained by this mechanism. (C) 2000 The Electrochemical Society. All right s reserved.