Consolidating the Oxygen Reduction with Sub-Polarized Graphitic Fe–N₄ Atomic Sites for an Efficient Flexible Zinc–Air Battery

Abstract

The effectuation of the Zn-air battery (ZAB) is appealing for active and durable catalysts to kinetically drive the sluggish cathodic oxygen reduction reaction (ORR). Atomic metal-N_<i>x</i>-C sites are widely witnessed with Pt-like activity, but their demetalations still severely restrict the durability in ORR. Here we have profiled an ordered hierarchical porous carbon supported Fe-N₄ single-atom (FeNC) catalyst by a template derivation method for efficient ORR and flexible ZAB studies. The FeNC structure is observed with a sub-polarized graphitic Fe-N₄ coordination with a shortened Fe-N bond for potentially consolidating the ORR, together with the hierarchical porous matrix for kinetical mass transfer. Resultantly, the optimized FeNC catalyst showcases Pt-beyond alkaline ORR activity (<i>E</i>_1/2 = 0.95 V) with long-term durability for 100 h, delivering the flexible ZAB device with high power density (251 mW cm^-2) and durable cycle life (80 h). This research underscores the criterion in rationalizing active and robust ORR catalysts through metal-nitrogen bond modulation.