Engineering adjacent Fe₃C as proton-feeding centers to single Fe sites enabling boosted oxygen reduction reaction kinetics for robust Zn-air batteries at high current densities

Oxygen reduction reaction (ORR) plays an important role in the next-generation energy storage technologies, whereas it involves the sluggish and complicated proton-coupled electron transfer (PCET) steps that greatly limit the ORR kinetics. Therefore, it is urgent to construct an efficient catalyst that could simultaneously achieve the rapid oxygen-containing intermediates conversion and fast PCET process but remain challenging. Herein, the adjacent Fe₃C nanoparticles coupling with single Fe sites on the bubble-wrap-like porous N-doped carbon (Fe₃C@Fe_SA-NC) were deliberately constructed. Theoretical investigations reveal that the adjacent Fe₃C nanoparticles speed up the water dissociation and serve as proton-feeding centers for boosting the ORR kinetics of single Fe sites. Benefiting from the synergistic effect of the Fe₃C and single Fe sites, the Fe₃C@Fe_SA-NC affords an excellent half-wave potential of 0.88 V, and enables the assembled Zn-air batteries with the high peak power density of 164.5 mW·cm⁻² and long-term stability of over 200 h at high current densities at 50 mA·cm⁻². This work clarifies the mechanism for improving ORR kinetics of single atomic sites by engineering the adjacent proton-feeding centers, shedding light on the rational design of cost-effective electrocatalysts for energy conversion and storage technologies.