A synergistic catalyst of C60-confined Ag3Fe2 and dual-metal sites for breaking the activity and stability trade-off for oxygen reduction

Abstract

The commercialization of zinc–air batteries (ZABs) is hindered by the sluggish kinetics of the cathodic oxygen reduction reaction (ORR). Guided by the hard and soft acid–base (HSAB) theory, this study successfully prepared the bimetallic catalyst FeAg–N–C via a stepwise pyrolysis strategy that combines low-temperature alloying and high-temperature nanoconfinement effects. The unique structure of the catalyst integrates hierarchically porous channels with multiscale synergy, atomically dispersed Fe–N₆ and Ag–N₅ sites, and in situ formed C₆₀@Ag₃Fe₂ core–shell nanoparticles, resulting in a pronounced synergistic catalytic effect. The hierarchical pores and high specific surface area (1270.56 m² g⁻¹) facilitate efficient mass and electron transport. The C₆₀@Ag₃Fe₂/MOF interface tailors the electronic density of the Fe and Ag single atoms through a strong electronic coupling, achieving precise control over their catalytic properties. Meanwhile, in situ Raman reveals that Fe strongly attracts electrons from O atoms, while Ag acts as an electron donor to stabilize the adsorption configuration, highlighting the effective Fe–Ag synergy. Electrochemical tests indicate that FeAg–N–C exhibits excellent ORR activity in both alkaline and acidic media. When assembled into a ZAB, it achieves a peak power density of 205 mW cm⁻², a specific capacity of 833 mAh g⁻¹ Zn, and remarkable stability over 300 hours and 900 cycles. This work not only demonstrates the feasibility of enhancing both activity and stability in bimetallic single-atom catalysts through multi-scale synergy, but also successfully overcomes the long-standing trade-off between activity and stability in conventional ORR electrocatalysts.