Boron-Doped Graphite Armoring and Regulating FeCo Dual-Site Alloy as Bifunctional Electrocatalyst for Long-Life Rechargeable Zn-Air Batteries

The dual-site alloy catalysts have wide applications in the field of catalysis due to their excellent synergistic effects and versatility. However, the activity and stability (especially the stability) of the dual-site alloy catalyst need to be further improved. Herein we report that a boron (B)-doped graphitic carbon with double effect has been used to modify the FeCo dual-site alloy catalyst. The synergistic structural features of FeCo dual-site alloy nanoparticles encapsulated within a boron-doped carbon matrix were unambiguously confirmed through high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) imaging and X-ray absorption spectroscopy (XAS) analyses. This unique architecture delivers exceptional bifunctional oxygen electrocatalytic performance, achieving a half-wave potential (E1/2) of 0.88 V vs RHE for oxygen reduction reaction (ORR) and requiring only 304 mV overpotential to reach 10 mA cm–2 during oxygen evolution reaction (OER) in 1.0 M KOH electrolyte. Significantly, the catalyst exhibits robust durability for over 60 h in the ORR, showing negligible activity loss at 0.75 V vs RHE. More significantly, it demonstrates more than 1000 h cyclic stability in the zinc-air battery (ZAB) test, surpassing the performance of the benchmark Pt/C+Ir/C. Theoretical calculation further reveals that B doping effectively lowers the d-band center of the catalytic site and reduces the energy barrier of the speed determination step, thereby enhancing the OER and ORR activity. This study establishes a new idea for the application of heteroatom-doped graphitic carbon supported non-noble metal dual-site alloy nanostructure catalysts in Zn-air batteries.