Graphene-wrapped ZnO nanospheres as a photocatalyst for high performance photocatalysis

In this work, graphene-wrapped ZnO nanospheres (ZnO-graphene nanocomposites) were prepared by a simple facile lyophilization method, followed by thermal treatment process. ZnO nanospheres with the size of about 100-400 nm, composed of numerous nanocrystals with hexagonal wurtzite structure, were well separated from each other and wrapped with transparent graphene sheets. Compared to ZnO nanospheres, the ZnO-graphene nanocomposites showed a significant enhancement in the photodegradation of methylene blue. This enhanced photocatalytic activity could be attributed to their favorable dye-adsorption affinity and increased optical absorption as well as the efficient charge transfer of the photogenerated electrons in the conduction band of ZnO to graphene. Thus, this work could provide a facile and low-cost method for the development of graphene-based nanocomposites with promising applications in photocatalysis, solar energy conversion, sensing, and so on.