Single-atom catalysts (SACs) have attracted extensive interest to catalyze the oxygen reduction reaction (ORR) in fuel cells and metal-air batteries. However, the development of SACs with high selectivity and long-term stability is a great challenge. In this work, carbon vacancy modified Fe-N-C SACs (FeH -N-C) are practically designed and synthesized through microenvironment modulation, achieving high-efficient utilization of active sites and optimization of electronic structures. The FeH -N-C catalyst exhibits a half-wave potential (E1/2 ) of 0.91 V and sufficient durability of 100 000 voltage cycles with 29 mV E1/2 loss. Density functional theory (DFT) calculations confirm that the vacancies around metal-N4 sites can reduce the adsorption free energy of OH*, and hinder the dissolution of metal center, significantly enhancing the ORR kinetics and stability. Accordingly, FeH -N-C SACs presented a high-power density and long-term stability over 1200 h in rechargeable zinc-air batteries (ZABs). This work will not only guide for developing highly active and stable SACs through rational modulation of metal-N4 sites, but also provide an insight into the optimization of the electronic structure to boost electrocatalytical performances.
Keywords: carbon vacancies; metal-organic frameworks; oxygen reduction reaction; single-atom catalysts; zinc-air batteries.
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