Pomegranate-Like FeNC with Optimized FeN 4 Configuration as Bi-Functional Catalysts for Rechargeable Zinc-Air Batteries.

Catalysts with FeNC moieties have demonstrated remarkable activity toward oxygen reduction reaction (ORR), but precise synthesis and configuration regulation of FeNC to achieve bi-functional catalytic sites for ORR and oxygen evolution reaction (OER) remain a great challenge. Herein, a pomegranate-like catalyst with optimized FeN 4 configuration is designed. The unique framework affords a large surface area for sufficient active site exposure and abundant macroporous channels for mass transport. By twisting chemical bonds, the electronic structure of FeN 4 is regulated, and the adsorption/desorption of oxygen species is facilitated. Compared to noble metal-based catalysts (Pt/C+IrO 2 ), the optimized FeNC exhibits impressive onset potential (0.96 V versus reversible hydrogen electrode), larger limiting current density (5.85 mA cm -2 ), and better long-term life for ORR, as well as, lower OER overpotential. When integrated into Zn-air batteries, it demonstrates a respectable peak power density (71.6 mW cm -2 ) and ideal cycling stability (30 h), exceeding that of commercial Pt/C+IrO 2 . The exploration offers a guideline for designing advanced bi-functional electrocatalysts.