Construction of N-doped hierarchically porous carbon catalysts with a CoFe alloy via spatial and chemical anchor confinement for the oxygen catalytic reaction

Abstract

This study presents a novel strategy for synthesizing bifunctional oxygen electrocatalysts by embedding CoFe alloy nanoparticles within N-doped hierarchically porous carbon (FeCo@NC) via spatial and chemical confinement effects. Utilizing the mixture of ZIF-67 and iron tetranitrophthalocyanine (FePc-NH₂) as precursors, the metal atoms' migration and agglomeration are effectively restricted during pyrolysis. By optimizing the Fe/Co atomic ratio, the Fe_0.46Co₁@NC catalyst achieves exceptional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities, evidenced by a high half-wave potential (E_1/2 = 0.86 V vs. RHE), a low overpotential gap (ΔE = 0.74 V), and a limiting current density of 5.8 mA cm⁻². Structural characterization confirms uniform dispersion of ∼10–20 nm FeCo alloy nanoparticles encapsulated by graphitic carbon layers, alongside abundant pyridinic/graphitic-N sites and hierarchical porosity (BET: 379 m² g⁻¹). When assembled in Zn–air batteries, Fe_0.46Co₁@NC delivers a high open-circuit voltage (1.46 V), a specific capacity of 781 mAh g⁻¹, and a peak power density of 168.4 mW cm⁻², which outperform the Pt/C + RuO₂ benchmarks. This work highlights the synergy between confined alloy nanoparticles and N-doped carbon matrices for advanced energy conversion.