N, S co-doped hollow carbon nanocages confined Fe, Co bimetallic sites for bifunctional oxygen electrocatalysis

Regulating pore architecture and electronic structure is of significance for improving oxygen electrocatalytic activity of M−N−C catalysts. Herein, N, S co-doped hollow carbon nanocages confined Fe, Co bimetallic sites (FeCo-NS-HNCs) are constructed through an efficient surface bridging strategy. The surface modifier of trithiocyanuric acid trisodium salt bridges Co doped ZIF-8 surface with Fe ions to promote the formation of Fe/Co-Nx sites. The synergistic coupling of metal sites and N, S co-doping manipulates the adsorption/desorption characteristics of M−Nx sites to optimize intrinsic activity. The Kirkendall effect constructs the hollow carbon nanocages, improving the accessibility of M−Nx sites. Benefiting from the ameliorated electronic structure and hollow porous architecture, FeCo-NS-HNCs displays excellent bifunctional oxygen electrocatalytic activity (ΔE = 0.655 V). The liquid and flexible Zn-air batteries of FeCo-NS-HNCs offer prominent power density and cycling stability. This work provides estimable insights into the structure design and activity regulation of M−N−C catalysts for Zn-air battery.