High Density Single Fe Atoms on Mesoporous N‐Doped Carbons: Noble Metal‐Free Electrocatalysts for Oxygen Reduction Reaction in Acidic and Alkaline Media

Abstract It remains a challenge to develop efficient noble metal‐free electrocatalysts for the oxygen reduction reaction (ORR) in various renewable energy systems. Single atom catalysts have recently drawn great attention as promising candidates both due to their high activity and their utmost atom utilization for electrocatalytic ORR. Herein, the synthesis of an efficient ORR electrocatalyst that is composed of N‐doped mesoporous carbon and a high density (4.05 wt%) of single Fe atoms via pyrolysis Fe‐conjugated polymer is reported. Benefiting from the abundant atomic Fe–N 4 sites on its conductive, mesoporous carbon structures, this material exhibits an excellent electrocatalytic activity for ORR, with positive onset potentials of 0.93 and 0.98 V in acidic and alkaline media, respectively. Its electrocatalytic performance for ORR is also comparable to that of Pt/C (20 wt%) in both media. Furthermore, it electrocatalyzes the reaction almost fully to H 2 O (or barely to H 2 O 2 ). Additionally, it is durable and tolerates the methanol crossover reaction well. Furthermore, a proton exchange membrane fuel cell and a zinc–air battery assembled using it on their cathode deliver high maximum power densities (320 and 91 mW cm −2 , respectively). Density functional theory calculation reveals that the material's decent electrocatalytic performance for ORR is due to its atomically dispersed Fe–N 4 sites.