Boosting the electrocatalytic activity of single atom iron catalysts through sulfur-doping engineering for liquid and flexible rechargeable Zn–air batteries

Abstract

Exploring effective electrocatalysts for the oxygen reduction reaction (ORR) is of great significance for rechargeable Zn–air batteries (ZABs). In particular, heteroatom-doping in metal-nitrogen-carbon single-atom catalysts (SACs) is considered an effective strategy to promote the electrocatalytic ORR. Herein, we report a practical strategy for designing single-Fe atom decorated S/N-doped carbon (Fe SAs@S/N–C) through the polymerization of phenylenediamine materials as an efficient ORR catalyst for ZABs. The introduction of S facilitates the high-density doping of Fe–N₄ active sites, and regulates the adsorption energy of oxygen-containing intermediates by altering the electronic structure of Fe–N₄ active sites. Benefiting from the S-doped carbon structure, the Fe SAs@S/N–C catalyst exhibits outstanding ORR performance (E_1/2 = 0.84 V) under alkaline conditions, possesses superior durability after 10 K cyclic voltammetry cycles and methanol resistance, outperforming the commercial 20 wt% Pt/C catalyst. Moreover, the Fe SAs@S/N–C catalyst can be easily synthesized at the gram scale, meeting the requirement of practical applications. The liquid-state ZABs assembled with the Fe SAs@S/N–C catalyst as the air cathode demonstrate a large peak power density of 156 mW cm⁻² and long-cycling over 300 h. Moreover, the as-assembled flexible all-solid-state ZABs exhibit excellent cycle stability under various bending conditions, demonstrating the promising potential of substituting Pt-based catalysts in practical applications.