Graphene/carbon nanospheres sandwich supported PEMfuel cell metal nanocatalysts with remarkably high activity and stability

Abstract

A new strategy to synthesize novel nano-sandwiched graphene/carbon/graphene (GCG) composites is described, employing the aqueous dispersion of low cost carbon nanospheres (CNS) in graphene oxide layers with subsequent thermal reduction. This 3D GCG sandwich shows a particular exfoliated graphene morphology, with CNS regularly embedded into the graphene nanosheets (GNS), from SEM and high-resolution TEM observations. The incorporation of CNS not only increases the Brunauer–Emmett–Teller (BET) surface area due to the effective expansion of the graphene interlayer, but also enhances the electrochemically accessible surface area and the charge transfer speed at the GCG–electrolyte interfaces due to a high density of between-plane electrolyte diffusion channels, that facilitate the reaction species transport and electron transport at high rates. As a result, this unique GCG nanoarchitecture with highly dispersed Pt particles exhibits a very high electrocatalytic activity for the oxygen reduction reaction (ORR). The half cell ORR mass activity of the Pt/GCG catalyst (17.7 A g⁻¹) is 2.2 times of that of Pt/GNS (8.2 A g⁻¹), and 3.8 times that of commercial Pt/C catalysts (4.6 A g⁻¹). Moreover, the Pt/GCG catalyst also shows excellent electrochemical stability. Therefore our new catalyst holds tremendous promise for potential applications in proton exchange membrane (PEM) fuel cells.