Effects of morphology and surface area of the oxide nanostructures on the visible–light induced generation of hydrogen in ZnO(TiO2)/Cd1 − xZnxS and ZnO(TiO2)/Pt/Cd1 − xZnxS heterostructures (x = 0.0, 0.2)

Abstract

Hydrogen can be generated by visible light irradiation of semiconductor heterostructures of the type ZnO/Pt/CdS and TiO2/Pt/CdS. In order to understand the dependence of hydrogen generation on the properties of the nanoparticles of ZnO and TiO2, we have carried out systematic studies. For this purpose, we have studied photocatalytic hydrogen generation by ZnO(TiO2)/Cd1−xZnxS and ZnO(TiO2)/Pt/Cd1−xZnxS (x=0.0, 0.2) heterostructures with oxide nanostructures possessing different morphologies and surface areas. In the case of TiO2/Pt/Cd0.8Zn0.2S heterostructures, the highest H2 evolution rate up to1.76mmolh−1g−1 were obtained with H2Ti3O7 nanotubes, with the least H2 evolution rate (0.55mmolh−1g−1) from TiO2 powder (Degussa P25). In the case of ZnO/Pt/CdS heterostructures, the highest H2 evolution rate (6.88mmolh−1g−1) were obtained from ZnO nanorods1, whereas the least H2 evolution rate (2.55mmolh−1g−1) was obtained from ZnO nanorods3. The photocatalytic activity of heterostructures generally follows the trend in BET surface areas of the oxide nanostructures, with high surface area favoring good hydrogen evolution activity.