Bismuth-Mediated Zinc Extraction-Induced Carbon Defects Boost Fe Single-Atom Catalysis for Efficient Oxygen Reduction.

Abstract

Fe single-atom catalysts with Fe-N4 configurations typically suffer from excessive adsorption of oxygenated intermediates, leading to intrinsic limitations in catalytic efficiency. Here, we propose a Bi-mediated Fe-adjacent Zn extraction strategy to create defects adjacent to Fe-N4 moieties on ZIF-8-derived carbon support, thereby tailoring the local microenvironment of Fe single atoms. The resulting Fe-N-pCd catalyst exhibits outstanding oxygen reduction reaction (ORR) activity in alkaline electrolyte, delivering a half-wave potential of 0.918 V versus RHE along with excellent durability. The assembled quasi-solid-state Zn-air battery using Fe-N-pCd as the air cathode catalyst affords stable operation for over 3000 h at -40°C. Mechanistic investigations demonstrate that the formed carbon defects adjacent to Fe-N4 sites redistribute the local electron density and favor the formation of an axial *OH-bound Fe state under ORR conditions. This defect-modulated coordination environment lowers the Fe d-band center and alleviates the overly strong Fe-*OH coupling, thereby changing the potential-limiting step from *OH removal to *OOH formation and accelerating ORR kinetics. This study provides a neighboring-template extraction route for engineering defect microenvironments adjacent to metal single atoms, opening new opportunities for the design of efficient ORR electrocatalysts.

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