Hierarchically porous Fe/N–C hollow spheres derived from melamine/Fe-incorporated polydopamine for efficient oxygen reduction reaction electrocatalysis

Fe/N–C catalysts show great potential for the oxygen reduction reaction (ORR) but their catalytic activity should be further improved for practical application. Here, we report a high performance Fe/N–C hollow sphere with excellent ORR activity in both alkaline and acidic solutions. It is synthesized via pyrolysis of a melamine/Fe-incorporated polydopamine nanosphere precursor at 800 °C in an argon atmosphere. The N-rich melamine in the precursor affords abundant N dopants to form dense Fe–Nx active sites and also facilitates the formation of micropores in the catalyst via the gasification effect, together improving the ORR activity. The as-reported Fe/N–C catalyst outperforms the Pt/C catalyst in basic media (45 mV more positive half wave potential), approaches the Pt/C catalyst in acidic media (55 mV lower half wave potential), and exhibits impressive performance in Zn–air primary batteries.