Effect of surface hydroxyl density on photocatalytic oxygen generation in aqueous TiO2 suspensions

Abstract

TiO₂ powders with various surface hydroxyl densities have been prepared by thermal treatment (600–1000 °C), and their activity for photocatalytic oxygen evolution in aqueous suspensions has been investigated in the presence of various electron acceptors, i.e. AgNO₃, K₂PtCl₄ and KBrO₃. The activity increased drastically with the thermal treatment. The oxygen evolution rate was found to be inversely proportional to the surface concentration of OH^–, indicating an inhibitory effect of surface hydroxyl groups with respect to photocatalytic oxygen evolution. On highly hydroxylated samples the formation of surface bound peroxides appears to be favoured over oxygen generation.