Regulation of the d band center and geometric distortion via an axial nitrogen strategy of the Fe–N–C oxygen electrocatalyst for a Zn–air battery

Abstract

The aqueous rechargeable Zn–air battery (ZAB) is regarded as a promising energy conversion device in view of its intrinsic safety and high energy density. However, the development of a highly efficient and long-term stable bifunctional catalyst remains challenging. Here, we developed a “one stone two birds” strategy to decrease the d band center of the Fe atom and mitigate the strain-induced distortion of the active site moiety by using an axial N atom construction on an atomically dispersed Fe atom-anchored carbon matrix catalyst. Theoretical studies and experimental characterizations reveal that, with the axial N atom, the Fe–N₅C catalyst exhibits weak adsorption strength to the reaction intermediate via an electron-withdrawing effect, and there is less geometric deformation of the planar Fe–N₄ configuration via counterbalancing the strain function. The dual-functional axial N atom demonstrates optimization of the Fe–N₄ active site. With the Fe–N₅C catalyst, the voltage gap between ORR and OER is narrowed to 0.64 V, and the ZAB is endowed with outstanding power density (128 mW cm⁻²) and energy density (1195 W h kg⁻¹ under 10 mA cm⁻²). The working life of the ZAB is extended to 330 h/1009 cycles, with a round-trip efficiency of up to 70.6%. In this regard, this work clarifies a modification strategy for preparing low-cost bifunctional oxygen electrocatalysts with high activity and long-term endurability.