Fe―N4 and Fe7Co3 Nanoalloy Dual-Site Modulation by Skeleton Defect in N-Doped Graphene Aerogel for Enhanced Bifunctional Oxygen Electrocatalyst in Zinc-air Battery

The dual-site electrocatalysts formed by metal single atoms combines with metal nanoparticles represent a promising strategy to enhance both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance. Herein, defect engineering is applied to dual-site ORR and OER electrocatalysts. Its design, synthesis, structural properties, and catalytic performance experimentally and theoretically are insightfully studied for the single-atomic Fe & horbar;N4 and the adjacent Fe7Co3 nanoalloy (FeCoNA) as dual-site loading on nitrogen-doped graphene aerogel (Fe & horbar;N/FeCo@NGA). The high-density dual-sites, together with the good electronic conductivity of NGA, synergistically improve the electronic structure for superior electrocatalytic activity. The half-wave potential of Fe & horbar;N/FeCo@NGA in ORR is 0.92 V and the overpotential of it in OER is 1.58 V. Corresponding all-solid-state Zn-air battery demonstrates a peak power density of 147.6 mW cm-2 and charge/discharge durability for over 140 h. Theoretical calculations reveal that the single-atomic Fe-N4 and FeCoNA dual-site on the skeleton defect optimized NGA, further refine the local electronic structure, modulating the tensile force on the O & horbar;O bond in *OOH intermediate, leading to its spontaneous dissociation and facilitating a significantly reduced energy barrier. This work takes a promising shortcut in the application of defect engineering for the development of highly efficient dual-site bifunctional oxygen electrocatalysts with single atoms.