Zinc- motivated Fe/Fe 5 C 2 /Fe 1- x S@Fe-N-C active sites grown on N-doped porous carbon toward efficient oxygen reduction reaction in zinc-air batteries.

The development of efficient non-precious metal oxygen reduction reaction catalysts to replace Pt-based catalysts is of great significance to accelerate the commercial application of fuel cells. In this study, a hierarchical porous carbon oxygen reduction reaction catalyst with Fe/FeC/FeS@Fe-N-C active sites was developed a simple and efficient solid-phase synthesis method. The introduction of zinc inhibited the growth and agglomeration of the nanoparticles and induced the formation of active nitrogen species and porosity, thus boosting the catalytic activity. The optimal FeZn-N-C-1 catalyst exhibited a high half-wave potential of 0.846 V, which is 24 mV higher than that of the commercial Pt/C, with a 4-e reaction path under alkaline conditions. When the FeZn-N-C-1 catalyst is employed as a cathode in a zinc-air battery, it achieves a high open circuit voltage of 1.54 V, power density of 143.6 mW cm and specific capacity of 804 mA h g.