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
Canhui Zhang, Xingkun Wang, Kai Song, Kaiyue Chen, Shuixing Dai, Huanlei Wang, Minghua Huang
Abstract
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@FeSA−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@FeSA−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.