Consolidating\nthe Oxygen Reduction with Sub-Polarized\nGraphitic Fe–N<sub>4</sub> Atomic Sites for an Efficient Flexible\nZinc–Air Battery

The effectuation of the Zn–air\nbattery (ZAB) is\nappealing\nfor active and durable catalysts to kinetically drive the sluggish\ncathodic oxygen reduction reaction (ORR). Atomic metal-N<sub><i>x</i></sub>-C sites are widely witnessed with Pt-like activity,\nbut their demetalations still severely restrict the durability in\nORR. Here we have profiled an ordered hierarchical porous carbon supported\nFe–N<sub>4</sub> single-atom (FeNC) catalyst by a template\nderivation method for efficient ORR and flexible ZAB studies. The\nFeNC structure is observed with a sub-polarized graphitic Fe–N<sub>4</sub> coordination with a shortened Fe–N bond for potentially\nconsolidating the ORR, together with the hierarchical porous matrix\nfor kinetical mass transfer. Resultantly, the optimized FeNC catalyst\nshowcases Pt-beyond alkaline ORR activity (<i>E</i><sub>1/2</sub> = 0.95 V) with long-term durability for 100 h, delivering\nthe flexible ZAB device with high power density (251 mW cm<sup>–2</sup>) and durable cycle life (80 h). This research underscores the criterion\nin rationalizing active and robust ORR catalysts through metal–nitrogen\nbond modulation.