ZnO rods/reduced graphene oxide composites prepared via a solvothermal reaction for efficient sunlight-driven photocatalysis

Small-sized ZnO rods with an average length of ca. 180 nm and a diameter of ca. 16 nm were successfully associated to reduced graphene oxide (rGO) via a solvothermal reaction conducted in ethanol. A set of characterization including TEM, SEM, XRD, BET, Raman spectroscopy and UV–vis absorption confirm that the ZnO/rGO composite is composed of highly dispersed ZnO rods bound to rGO nanosheets. The photocatalytic activity of the ZnO/rGO composite was investigated under solar light and under visible light irradiation using the Orange II dye in aqueous solution. Results indicate that the ZnO/rGO composite containing 10 wt% rGO used under solar light irradiation exhibit the highest photocatalytic activity and that the kinetic of reduction is of pseudo-fist-order. The photocatalyst is only weakly sensitive to pH changes and to the presence of inorganic salts or to glucose in the reaction medium. In addition, the reusability of the ZnO/rGO composite was studied and the results demonstrate that the photocatalyst can be reused up to fifteen times with nearly negligible loss of activity. The high photocatalytic performances can be attributed to the high specific surface of ZnO rods, to the enhanced visible light absorption of the ZnO/rGO composite and to the strong decrease of charge carrier recombinations originating from the association of ZnO rods with rGO.