High Durability of Fe-N-C Single-Atom Catalysts with Carbon Vacancies toward the Oxygen Reduction Reaction in Alkaline Media

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 (Fe-H-N-C) are practically designed and synthesized through microenvironment modulation, achieving high-efficient utilization of active sites and optimization of electronic structures. The Fe-H-N-C catalyst exhibits a half-wave potential (E-1/2) of 0.91 V and sufficient durability of 100 000 voltage cycles with 29 mV E-1/2 loss. Density functional theory (DFT) calculations confirm that the vacancies around metal-N-4 sites can reduce the adsorption free energy of OH*, and hinder the dissolution of metal center, significantly enhancing the ORR kinetics and stability. Accordingly, Fe-H-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-N-4 sites, but also provide an insight into the optimization of the electronic structure to boost electrocatalytical performances.

Automated summary

In this study, carbon vacancy modified Fe-N-C single-atom catalysts (Fe-H-N-C) were designed and synthesized through microenvironment modulation, resulting in high selectivity and long-term stability. The Fe-H-N-C catalyst exhibited a high half-wave potential and durable performance. This work provides guidance for developing highly active and stable single-atom catalysts and insights into optimizing electronic structures to enhance electrocatalytic performances.