Synthesis of three-dimensional Au-graphene quantum dots@Pt core–shell dendritic nanoparticles for enhanced methanol electro-oxidation

Abstract

Au-graphene quantum dots (GQDs)@Pt core–shell nanodendrites are synthesized through a two-step reduction approach, in which Au forms the core, GQDs form an intermediate layer and dendritic Pt forms the shell. Among the above synthesized catalysts, the GQDs can manipulate the binding of reaction intermediates on the Pt surface as well as assemble π–π* conjugate bonds, thus forming a dendritic Pt shell instead of a compact Pt shell. The obtained core–shell structure was characterized by transmission electron microscopy, energy-dispersive x-ray and x-ray photoelectron spectroscopy. The methanol electro-oxidation was investigated in alkaline media on the Au-GQDs@Pt modified electrode via cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy analysis. In particular, we discovered that Au–Pt assembled with GQDs could dramatically improve the activity and stability of the catalysts, owing to the synergistic effect raised by the GQDs, which exhibit prominent electron conductivity and great chemical/physical stability. It was also found that the Pt/Au mole ratios could control the Pt shell thickness, which significantly affected the catalytic methanol oxidation activity of the Au-GQDs@Pt nanodendrites. The Au-GQDs@Pt nanodendrites with optimum Pt/Au mole ratios of 1.0 exhibited a 2.5 times increase in electrocatalytic activity toward methanol oxidation compared with the commercial catalyst (Pt/C), and its CO tolerance was also greatly improved. The above results show that the Au-GQDs@Pt nanocatalysts have potential application prospects in direct methanol fuel cells.