Fe(CN)5@PIL-derived N-doped porous carbon with FeCxNy active sites as a robust electrocatalyst for the oxygen reduction reaction

Abstract

The synthesis and catalytic mechanism of new-type Fe–N co-doping catalysts are important topics for the research on fuel cells. Herein, we report the synthesis and oxygen reduction reaction (ORR) properties of a new Fe–N co-doping carbon composite using poly(ionic liquid)s and ferric salt as precursors. The structural characterizations revealed that the as-prepared material features ordered porous properties with a specific surface area of 719.1 m² g⁻¹, corresponding to FeC_xN_y/N-doped porous carbons (FeC_xN_y/N-PC). The electrochemical measurements indicated they show superior catalytic activity (Tafel slope of 70.8 mV dec⁻¹ and E_1/2 of 0.84 V), stability and high methanol tolerance compared to the commercial Pt/C catalyst. Furthermore, density functional theory calculations uncovered that the FeC_xN_y/N-PC composite catalyzes the ORR according to the four-electron associative mechanism with the free-energy barrier of 0.51 eV in the rate-determining formation of H₂O. Interestingly, the electronic structure analysis demonstrated the FeC_xN_y particles serve as active sites and the synergistic effect of the Fe and N atoms of N-PC can promote the ORR performance.