A Janus dual-atom catalyst for electrocatalytic oxygen reduction and evolution

Dual-atom catalysts, which exhibit high activity and atom utilization, show promise for sustainable energy conversion and storage technologies. However, the rational design and synthesis of a dual-atom catalyst with structurally homogeneous and flexible active sites remains challenging. In this work, we developed a strategy for the synthesis of a carbon-based catalyst with diatomic Fe–Co sites in which the Fe and Co atoms are coordinated to N and O atoms, respectively, and linked through bridging N and O atoms (FeCo–N₃O₃@C). The Janus FeCo–N₃O₃@C quaternary dimer is a stable and efficient bifunctional catalyst in the electrocatalytic oxygen reduction reaction (half-wave potential E_1/2 = 0.936 V) and oxygen evolution reaction (potential E = 1.528 V at 10 mA cm⁻²). When assembled in a Zn–air battery, it exhibits superior performance over a benchmark Pt/C + RuO₂ air cathode. A series of ex situ and in situ characterizations, combined with theoretical calculations, revealed that the bifunctional performance of the catalyst originates from the strong coupling of the Fe–N₃ and Co–O₃ moieties, which alters the d-orbital energy level of the metal atoms, optimizing the adsorption–desorption of oxygenated intermediates and improving the reaction kinetics of the oxygen reduction and evolution reactions. The in-depth insights gained into the fundamental mechanism of this dual-atom catalyst at the atomic and electronic level will facilitate the rational design of further highly efficient multifunctional catalysts with customized activities for specific reactions.