Copper nanoparticle@graphene composite arrays and their enhanced catalytic performance

Noble metal nanoparticles have been widely investigated for catalysis, while the source of noble metal is limited. Copper nanoparticles are the ideal candidates for replacing noble metal nanoparticles in the specific catalysis field. However, Cu NPs from traditional methods are generally nonuniform in morphology and wide distribution in size. In this work, a simple method is developed to fabricate uniform copper nanosphere arrays on a large scale (∼cm ² ) using monolayer colloidal crystals as templates. A reduced graphene oxide (rGO) is further introduced on the surfaces of Cu nanospheres to form the Cu NPs@rGO core-shell structured arrays on the substrates by the redox reaction. The rGO shell can protect the Cu NPs from oxidation, which guarantees the good stability of Cu@rGO nanoparticle arrays. The obtained Cu@rGO core-shell arrays (periodic length: 350 nm, diameter: 110 nm) exhibit excellent catalytic performance towards the reduction of 4-nitrophenol to 4-aminophenol, which is 14 times larger than that of Au nanoparticles as previously reported. With decreasing the length of periodicity of Cu@rGO core-shell array, its catalytic activity increases. When the periodicity is fixed, with increase of Cu NP size, the value of activity factor k is decreasing. More importantly, such Cu@rGO core-shell arrays on the supporting substrates can be easily recycled for the catalytic reaction. These Cu@rGO arrays have also other potential applications in SERS, electrochemistry, biosensor, etc.