Fe–N–C catalyst with atomic Fe dispersion and hierarchical porosity via PVP-assisted MOF synthesis for ORR in acidic media

Abstract

Iron–nitrogen–carbon (Fe–N–C) catalysts have emerged as leading non-precious metal catalyst (NPMC) candidates for the oxygen reduction reaction (ORR) in acidic media, yet challenges persist in achieving high activity, durability, and atomic-scale Fe dispersion. Here, we report Fe-ZIF-8-PVP-1000, a high-performance Fe–N–C catalyst synthesized via a polyvinylpyrrolidone (PVP)-assisted metal–organic framework (MOF) strategy. PVP functions as a morphology stabilizer, nitrogen dopant, and metal dispersant, producing atomically dispersed Fe–N_x sites within a hierarchically porous, nitrogen-rich carbon matrix. The catalyst achieves a half-wave potential (E_1/2) of 0.865 V vs. RHE in 0.5 M H₂SO₄, surpassing commercial 28.6 wt% Pt/C (E_1/2 ≈ 0.855 V) and rivaling the best Fe–N–C catalysts reported to date. With a BET surface area of 1579.8 m² g⁻¹ and a micropore volume of 0.54 cm³ g⁻¹, it provides abundant accessible active sites; electrochemical analysis further revealed an electron transfer number of n ≈ 3.96 with minimal H₂O₂ yield, confirming a highly selective four-electron ORR pathway. The catalyst retained approximately 84% of its current after 10 h and exhibited only an 11 mV negative shift in E_1/2 after 30 000 cycles, demonstrating outstanding stability. This scalable synthesis provides acid-tolerant, high-performance NPMCs with optimized structural and electronic properties.