Hierarchically porous graphene sheets and graphitic carbon nitride intercalated composites for enhanced oxygen reduction reaction

Abstract

The electrocatalytic activity of graphitic carbon nitride (GCN), a potential metal-free alternative to the conventional platinum-based catalysts for oxygen reduction reaction (ORR), is restricted by its poor electrical conductivity. Introducing conductive carbon substrates can enhance the ORR performance of GCN, but until now, none of the carbon-supported GCN catalysts has shown both excellent catalysis selectivity and fast ORR kinetics. Two-dimensional graphene sheets (GSs) may serve as suitable substrates for GCN due to their fast electron collection and transport properties, and their structural similarity to GCN as well. In this work, we present a facile method of producing intercalated GS/GCN composites with hierarchical porosity, which is experimentally achieved for the first time. The ORR activity is optimised by tuning the amount of active sites, electrical conductivity and mass transport. The obtained material possesses 100% catalysis selectivity towards the four-electron pathway, and its ORR activities outperform any other existing GCN-based catalysts. It also shows significantly improved tolerance against methanol and enhanced long-term stability, compared with the commercial platinum-loaded carbon catalysts. Thus it is expected that the hierarchically porous GS/GCN intercalated composite is a promising future ORR catalyst.