CeO2-decorated reduced graphene oxide for lubricative, anticorrosive and photocatalytic purposes

Abstract

CeO2 decorated reduced graphene oxide (CeO2@rGO) nanocomposites synthesized using a hydrothermal method were studied for their tribological, anti-corrosive and photocatalytic applications. Results showed that CeO2 nanoparticles with an average diameter of ∼12.24 nm were uniformly distributed and covalently bonded onto the surface of rGO. When the nanocomposites were added into PAO5w-40 lubricating oil, the coefficient of friction in the friction test was 31.9% lower than that using the pure lubricating oil. The corresponding wear mechanism was changed from oil-film lubrication to reaction film lubrication, which is mainly attributed to the filling effect of nanostructured CeO2 powers and lubrication effect of rGO. The nanocomposites were also added into chromium-free Dacromet coating and the corrosion current density in the corrosion test was decreased by an order of magnitude. This is mainly due to the formation of various chemical bonds and passivation layer on the modified coating, which improves its density. It is also attributed to the uniformly dispersed rGO, which forms a conductive channel, resulting in the preferred corrosion of the Zn–Al alloy in the coating thus achieving an effective protection effect to the substrate. When the composites were applied as the photocatalyst in an RhB solution under the irradiation of ultraviolet light, the RhB dye was effectively removed with an efficiency up to 90.5%, because the rGO can extend the life time of active electron-hole pairs and prevent CeO2 nanoparticles from severe agglomeration.