Universal Synthesis of Half-Metallic Diatomic Catalysts for Efficient Oxygen Reduction Electrocatalysis.

Developing efficient and low-cost noble-free metal electrocatalysts is an urgent requirement. Herein, a one-step, solid-state template-assisted method for fabricating isolated half-metallic diatomic M, Zn─N─C (M═Fe, Co, and Ni) catalysts is reported. In particular, the fabricated Fe, Zn─N─C structure exhibits superior oxygen reduction reaction capabilities with a half-wave potential of 0.867 V versus RHE. The Mossbauer spectra reveal that the Fe, Zn─N─C half-metallic diatomic catalyst has a large proportion of the D2 site (ferrous iron with a medium spin state). Density functional theory (DFT) reveals that in Fe, Zn─N─C structures, the zinc sites play a unique role in accelerating the protonation process of O2 in ORR. In assembled zinc-air batteries, a maximum power density of 138 mW cm-2 and a capacity of 748 mAh g zn-1 can be obtained. This work fabricates a series of efficient M, Zn─N─C diatomic electrocatalysts, and the developed solid-state reaction method can hopefully apply in other energy conversion and storage fields.