Efficient sunlight-driven photocatalytic activity of chemically bonded GNS–TiO2 and GNS–ZnO heterostructures

Abstract

Recently, Graphene nanosheets (GNS) decorated semiconductor photocatalysts have received more attention because of their enhanced photocatalytic activity caused by their varying band gap energy and interfacial charge transfer effect. However, the effects of band gap variation and interfacial charge transfer are rarely involved in the chemical bonding formation between GNS and semiconductors. In this paper, we report the fabrication of GNS–TiO₂ and GNS–ZnO nanostructures with a chemically bonded interface using the modified Hummers method. The chemically bonded GNS–TiO₂ and GNS–ZnO nanostructures greatly enhanced their photocatalytic activity in the photodegradation of methylene blue (MB) dye, which was performed in an aqueous medium. The band gap energy value of the GNS–TiO₂ and GNS–ZnO was found to be 1.39 eV and 1.26 eV, respectively, confirmed by UV-DRS analysis. The enhancement in the photocatalytic activity was attributed to the synergetic effect and also to the chemical bonding between the GNS-semiconductor interfaces. It remarkably decreased the recombination rate and also increased the number of holes participating in the photodegradation process, as confirmed by XPS analysis. This work can provide a revelation for designing new heterogeneous photocatalysts, which can be used in energy, water splitting, and environmental cleaning applications.