Coordination polymer-induced interface engineering for high-density dual-Fe oxygen reduction catalysts in Zn–Air batteries

Abstract

Although dual-atom catalysts exhibit cooperative activity beyond single-atom catalysts, practical syntheses that deliver both high metal loading and atomically defined proximal sites remain scarce. Prevailing approaches rely on extensive defect engineering or multistep confinement, which are experimentally demanding, difficult to scale, and often mechanistically unclear. Herein, a polymer-interface-assisted strategy is introduced to construct dual-Fe sites embedded in nitrogen-doped carbon frameworks. The polymer-derived interface ensures full coordination of surface Zn and generates abundant nitrogen functionalities and defects during pyrolysis, enhancing the density and spatial proximity of Fe coordination sites. The resulting material contains atomically dispersed dual-Fe centers, which enable electronic coupling and accelerate the kinetics of the oxygen reduction reaction. The catalyst exhibits a high half-wave potential of 0.91 V, near-zero peroxide yield, and outstanding durability. In a Zn–air battery, it delivers a peak power density of 182 mW cm−2 and stable long-term cycling. Density functional theory calculations indicate that the dual-Fe moiety with pre-adsorbed hydroxide ions facilitates a dissociative oxygen pathway with an overpotential of only 0.24 eV, outperforming FeN4 single-atom sites due to the cooperative configuration of adjacent Fe atoms. This study presents a robust interface-engineering approach for the formation of dual sites and emphasizes the role of local coordination symmetry in enhancing catalytic efficiency.