An Fe–N–C electrocatalyst with dense active sites synthesized by expeditious pyrolysis of a natural Fe–N4 macrocyclic complex

Abstract

Platinum group metal (PGM)-free ORR catalysts containing highly dispersed metal–nitrogen sites have been demonstrated as the most promising alternatives to Pt-based catalysts. However, it remains a tremendous challenge to synthesize efficient ORR catalysts with dense active sites expeditiously. Herein, a series of highly dispersive Fe–N–C catalysts derived from N-doped Ketjen Black (N-KJB) and hemin were synthesized by a simple rapid pyrolysis method within 1 min. Benefitting from the spatial confinement effect of N-KJB and high-coordination natural iron source, the highly dispersive Fe is higher than 3 wt% without Fe particle agglomeration. The optimized Fe-KJB-3-60A electrocatalyst exhibits a superior ORR activity with a half-wave potential of 0.90 V in 0.1 M KOH and 0.79 V in 0.1 M HClO₄. When used as the cathode catalyst in Zn–air batteries and proton exchange membrane fuel cells, Fe-KJB-3-60A exhibits a maximum peak power density of 251 mW cm⁻² and 348 mW cm⁻², respectively.