Defective Fe3O4‐x Few‐Atom Clusters Anchored on Nitrogen‐Doped Carbon as Efficient Oxygen Reduction Electrocatalysts for High‐Performance Zinc–Air Batteries

Abstract It remains a challenge to develop cost‐effective, high‐performance oxygen electrocatalysts for rechargeable metal–air batteries. Herein, zinc‐mediated zeolitic imidazolate frameworks are exploited as the template and nitrogen and carbon sources, onto which is deposited a Fe 3 O 4 layer by plasma‐enhanced atomic layer deposition. Controlled pyrolysis at 1000 °C leads to the formation of high density of Fe 3 O 4‐ x few‐atom clusters with abundant oxygen vacancies deposited on an N‐doped graphitic carbon framework. The resulting nanocomposite (Fe 3 O 4‐ x /NC‐1000) exhibits a markedly enhanced electrocatalytic performance toward oxygen reduction reaction in alkaline media, with a remarkable half‐wave potential of +0.930 V versus reversible hydrogen electrode, long‐term stability, and strong tolerance against methanol poisoning, in comparison to samples prepared at other temperatures and even commercial Pt/C. Notably, with Fe 3 O 4‐ x /NC‐1000 as the cathode catalyst, a zinc–air battery delivers a high power density of 158 mW cm −2 and excellent durability at 5 mA cm −2 with stable 2000 charge–discharge cycles over 600 h. This is ascribed to the ready accessibility of the Fe 3 O 4‐ x catalytic active sites, and enhanced electrical conductivity, oxygen adsorption, and electron‐transfer kinetics by surface oxygen vacancies. Further contributions may arise from the highly conductive and stable N‐doped graphitic carbon frameworks.