Synthesis of Pt nanoparticles anchored on graphene-encapsulated Fe3O4 magnetic nanospheres and their use as catalysts for methanol oxidation

Reduced graphene oxide (rGO)-encapsulated amine functionalized Fe3O4 magnetic nanospheres (AMs), were used to support Pt catalysts (Pt-rGO-AMs). The Pt-rGO-AMs were fabricated by modifying positively-charged aminopropyltrimethoxysilane on the surface of Fe3O4 nanoparticles (NPs) to form functionalized Fe3O4 NPs. Then negatively-charged graphene oxide (GO) was coated on the surface of the functionalized Fe3O4 nanospheres by electrostatic layer-by-layer self-assembly. Finally, Pt NPs were uniformly anchored on the surface of GO by a polyol reduction reaction and the GO was simultaneously reduced to rGO. The Pt-rGO-AMs exhibit excellent ferromagnetic property, which makes it possible to realize controllable on–off reactions and convenient recycling of catalyst materials. The electrochemical activity of the catalyst for methanol oxidation is significantly improved compared to Pt NPs absorbed on a rGO sheet and has better stability. The superior performance of this Pt-rGO-AMs catalyst is attributed both to the structure, which improve the accessibility of the Pt NPs by exposing them on the surface of the support, and to the greatly improved electronic conductivity of the support.