Boosting oxygen reduction and Zn–air battery performance via the rational design of interlayer pyridinic nitrogen in Zn-N4-hierarchical porous carbon nanofibers

Abstract

Zn–N–C catalysts demonstrate exceptional oxygen reduction reaction (ORR) performances due to their distinct electronic and geometric configurations. However, the atomic coordination configuration of the Zn sites remains frequently underexplored compared to conventional strategies focusing on Zn loading, surface engineering, or ligand modifications. Herein, atomically dispersed Zn-N₄ is embedded within hierarchical porous carbon nanofibers (Zn-N₄-HPCNFs) based on surfactant orientation and electrospinning, which is influenced by surfactant and ligand effects. The X-ray absorption spectra validate the atomic dispersion of Zn-N₄ moieties in Zn-N₄-HPCNFs. Despite the low Zn content (0.327 wt%), the Zn-N₄-HPCNFs catalyst exhibits a high half-wave potential (0.88 V), a low Tafel slope (53 mV dec⁻¹), and a remarkable durability (99% current retention). Operando electrochemical infrared spectroscopy and density functional theory calculations demonstrate the Zn-N₄-interlayer pyridinic nitrogen provides the lowest free energy barrier for *OOH formation, which represents the rate-limiting step. When integrated into Zn–air batteries, Zn-N₄-HPCNFs catalyst achieves an exceptional performance, achieving a peak power density of 130.2 mW cm⁻² and a specific capacity of 855 mA h g⁻¹ with sustained stability exceeding 300 h, significantly surpassing 20 wt% Pt/C benchmarks. This work provides both an efficient bifunctional catalyst and fundamental insights into atomic coordination engineering for advanced electrocatalysts.