▎ 摘　　要

This work aims to investigate the underlying mechanism in the great enhancement of photocatalytic activity when involving graphene. With the introduction of reduced Graphene Oxide (rGO) to ZnO nanoparticles (ZnONPs) by a simple mechanical mixing method, ZnO nanoparticles-reduced Graphene Oxide hybrids (ZnO-rGO) perform significantly better than pure ZnONPs in the degradation of methyl blue (MB) under UV light condition. However, our experiments demonstrated if allowing the MB non-covalently attached on rGO first, the photodegradation of ZnONPs on MB is actually interfered and slowed by the presence of rGO. Combined with these two facts, we concluded that rather than directly participating in the photodegradation of dyes, the rGO in ZnO-rGO hybrids preferentially accepts the photo-generated electrons as an electron reservoir, significantly reduces the chances of the recombination, and effectively prolongs the lifetime of holes in ZnONPs, therefore greatly enhancing the efficiency of hole-induced decomposition of dyes. The photodegradation process induced by ZnO-rGO photocatalyst still mainly occurs on the surface of ZnONPs instead of rGO. Our findings help to understand the role of rGO in improved photocatalytic property in ZnO-rGO system and provide new strategies for developing novel photocatalysts. (C) 2012 Elsevier B.V. All rights reserved.