Dual-Role Zn Engineering Enables Electron Redistribution and Hierarchical Porosity in Co-N4 Carbon Nanofibers for Efficient Zinc-Air Batteries

Abstract

Developing bifunctional oxygen electrocatalysts with both high intrinsic activity and efficient mass transport remains a key challenge for rechargeable zinc-air batteries (ZABs). Herein, a dual-role Zn engineering strategy is developed to simultaneously regulate the electronic structure and construct hierarchical porosity in Co-N4 carbon nanofibers (Zn/Co-N@CNF). During the electrospinning-pyrolysis process, Zn acts as an electronic regulator that modulates the electronic environment of neighboring Co-N4 sites, inducing electron redistribution and a downward shift of the Co d-band center to -3.43 eV, thereby optimizing the adsorption energetics of oxygen intermediates. Meanwhile, Zn evaporation serves as a dynamic porogen that promotes the generation of highly dispersed Co sites and induces the formation of hierarchical pores, facilitating mass transport and maximizing active-site accessibility. First-principles calculations reveal that the Zn-N4/Co-N4 sites enable optimized oxygen-intermediate adsorption, leading to ultralow theoretical ORR/OER overpotentials of 0.37/0.43 V. Benefiting from this structural-electronic synergy, Zn/Co-N@CNF exhibits excellent bifunctional oxygen electrocatalytic performance with a low Delta E of 755 mV. When employed as an air cathode, the assembled ZAB delivers a high peak power density of 303 mW cm- 2 and remarkable cycling stability exceeding 1150 h without an additional carbon diffusion layer. This work establishes a dual-role metal engineering strategy that integrates electronic modulation with hierarchical porosity for constructing high-performance air electrodes for next-generation zinc-air batteries.