Engineering the electronic structure of isolated manganese sites to improve the oxygen reduction, Zn-air battery and fuel cell performances

Single-atom manganese catalysts possess high stability in the oxygen reduction reaction (ORR) due to their lower Fenton reaction activity. Here, we employ N- and S-co-coordination strategy to modulate the microstructural Mn sites towards high-efficiency ORR. The fabricated Mn-N/S-C catalyst with isolated Mn-N2S2 sites demonstrates a positive half-wave potential of 0.91 V for the ORR. The fabricated zinc-air battery with Mn-N/S-C as the cathode affords a maximal power density of 193 mW cm-2 and superior output stability. Moreover, the maximal power density is increased by 1.53 times compared with S-free Mn-N-C catalyst in anion exchange membrane fuel cells (AEMFCs). Both experimental characterizations and theoretical simulations unveil that the main active sites in the Mn-N/S-C should be Mn-N2S2 moiety embedded into the graphene framework (Mn-N2S2G). Further computational results demonstrate that the S atom doping and asymmetry of structure lead to higher ORR activities of ortho-Mn-N2S2G than Mn-N4G, Mn-N3SG, para-Mn-N2S2G and Mn-NS3G.