Investigation of the OH-Radical Formation for the Visible-light Irradiated BiVO 4 - TiO 2 , BiVO 4 - SnO 2, and UV-light Irradiated BiVO 4 - ZnO Nanocomposite Photocatalytic Films: Roles of Photocatalytic Reduction Channels

Abstract

Abstract Many attempts for developing the BiVO4 photocatalysts by coupling with other metal oxide semiconductors with appropriate band potentials have been performed by many researchers to improve the separation of photogenerated electron-hole pairs and increase the charge carrier lifetimes. In the present work, the OH radical formation of the nanocomposite photocatalysts of visible light responsive BiVO4 with other semiconductor photocatalysts such as particulate TiO2, SnO2, and ZnO was investigated. The OH radical formation by the photocatalytic reduction reaction of H2O2 on the TiO2 surface has already been proposed by several researchers. Here, the possible roles of OH radical formation by the reduction reaction of H2O2 on the photocatalytic surfaces of the BiVO4 – X (X =TiO2, SnO2, and ZnO) nanocomposite photocatalysts were also examined by investigating the effects of H2O2 on the amount of the OH radicals formed by the photocatalytic reactions. Finally, experiments of degassing oxygen in the visible light irradiated BiVO4 -TiO2, BiVO4 -SnO2, and UV-irradiated BiVO4 -ZnO nanocomposite photocatalysts were performed to investigate the relative roles of reaction channels of OH radical formation of (a) the direct reduction of H2O2 and (b) indirect reduction reaction of H2O2 via superoxide radical anion (･O2-). It was found that there were differences in the relative roles of OH radical formation by the reaction channels of (a) and (b) for the visible light irradiated BiVO4 and in the visible light irradiated BiVO4 -TiO2, BiVO4 -SnO2, and UV-irradiated BiVO4 -ZnO nanocomposite photocatalysts.