Graphene–Ag/ZnO nanocomposites as high performance photocatalysts under visible light irradiation

[Display omitted] •Synthesis of Graphene–Ag/ZnO composite photocatalysts by facile one-step nontoxic approach.•Enhanced visible light absorption and efficient charge separation of ZnO by graphene modification and silver doping.•Effective utilization of photo-induced conduction band electron and valance band hole to photocatalytic degradation process.•Excellent photocatalytic performance of composites over pure ZnO.•The reduction in COD and TOC confirms the destruction of the organic molecules in the effluents along with colour removal. Visible-light-responsive Graphene–Ag/ZnO nanocomposites were fabricated using a facile, one-pot, nontoxic solvothermal process for the photodegradation of organic dyes. During the solvothermal process reduction of graphene oxide and loading of Ag-doped ZnO nanoparticles on two-dimensional graphene sheets were achieved. Electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, BET surface area measurements, X-ray photoelectron spectroscopy and powder X-ray diffraction were used to confirm that the Ag-doped ZnO nanoparticles as randomly dispersed and effectively decorated on graphene sheets via covalent bonds between Zn and C atoms. Optical properties studied using UV–vis diffuse reflectance spectroscopy confirmed that the absorption edge of Ag-doped ZnO shifted to visible-light region with the incorporation of graphene. The as-synthesized Graphene–Ag/ZnO nanocomposites showed unprecedented photodecomposition efficiency compared to the Ag-doped ZnO, pristine ZnO and commercial ZnO under visible-light. The textile mill effluent containing organic substances was also treated using photocatalysis and the reduction in the chemical oxygen demand (COD) of the treated effluent revealed a complete destruction of the organic molecules along with colour removal. This dramatically enhanced photoactivity of the composite which is attributed to retarded charge recombination rate, great adsorption of dyes, enhanced visible light absorption and fast transfer processes. This research has the potential to provide new avenues for the in situ fabrication of the Graphene–Ag/ZnO composites as highly efficient photocatalysts.