Effect of secondary heteroatom (S, P) in N-doped reduced graphene oxide catalysts to oxygen reduction reaction

Abstract

• Straightforward strategy to fabricate N,S-and N,P-dual-doped graphene electrocatalyst. • Ammonium sulphate and ammonium monohydrogenphosphate are the heteroatoms salt precursors. • Higher promotional effect of S compare to P in ORR in alkaline media. • Synergistic effect from the combination of the N, S heteroatoms and surface structure. Heteroatomic dual-doped metal free graphene materials have revealed significant improvement in the electrocatalysis properties for oxygen reduction reaction (ORR) in alkaline anion exchange membrane fuel cells. Here we report a straightforward and cost-effective strategy to fabricate N, S- and N, P- dual-doped reduced graphene oxide electrocatalysts, characterized by similar N/S and N/P ratios. For this purpose, we used ammonium sulfate ((NH 4 ) 2 SO 4 ) and ammonium monohydrogenphosphate ((NH 4 ) 2 HPO 4 ) as heteroatom precursors to obtain the desired catalysts by pyrolysis with graphene oxide. Systematic characterization reveals that the secondary heteroatom S has a greater promotional effect than P in ORR. Furthermore, the gap between the onset potentials of N, S- dual-doped graphene and the standard Pt/C is only 30 mV. The results imply that the combination of the N, S heteroatoms and the surface structure in dual-doped reduced graphene oxide lead to a synergistic effect in catalyzing ORR in alkaline media.