The Synergistic Effect of Iron Triatomic Clusters and Fe ₃ C Nanoparticles Enhances Oxygen Reduction Reaction Performance in Zinc–Air Batteries

Iron-based catalysts are considered promising replacements to replace traditional Pt-based catalysts for the oxygen reduction reaction (ORR). Nevertheless, their limited intrinsic activity and unsatisfactory stability hinder their practical applications. Herein, a highly efficient ORR catalyst of FeFACs/FeNPs–N–C is synthesized by codoping of Iron triatomic clusters (FeFACs) and Fe3C nanoparticles (FeNPs) onto a porous and highly graphitized nitrogen-doped carbon (NC) substrate via high-temperature pyrolysis. The composite catalyst displays excellent ORR activity with half-wave potentials (E1/2) of 0.817 V in acidic and 0.915 V in alkaline media. Meanwhile, density functional theory (DFT) simulations clarify the ORR catalytic mechanism, especially the role the incorporated FeFACs played in the catalytic. The calculation results show that the synergistic effect between FeFACs and FeNPs species can disrupt the localization of Fe 3d orbitals, improve the electronic conductivity, and lower the ORR overpotential of the active center, thus facilitating the ORR path. Besides, the FeFACs/FeNPs–N–C-based zinc air battery (ZAB) possesses remarkable advantages such as high power density (230.3 mW cm–2), large specific capacity (807.5 mA h gzn–1), and extremely long cycle life (>350 h). This work provides valuable insights into the construction of few atomic cluster/nanoparticle catalysts for efficient energy conversion devices.