Boosting activity toward oxygen reduction reaction of a mesoporous FeCuNC catalyst via heteroatom doping-induced electronic state modulation

Abstract

Non-precious metal catalysts for oxygen reduction reaction (ORR) are promising alternatives to Pt/C in fuel cells, thus, demand for advanced catalysts is arising. Herein, we prepared and characterized mesoporous Fe and Cu anchored in N-, S-, and P-doped carbon (FeCu_xNC) catalysts, revealing the presence of ordered mesoporous grain-shaped particles and demonstrating that the electronic state of the active sites (Fe–N_x) is controlled by their environments, which can affect ORR kinetics. Half-cell measurements revealed that FeCu_xNC promoted ORRs more effectively (0.92 V at 3 mA cm⁻²) than Pt/C (0.87 V at 3 mA cm⁻²) in alkaline conditions, while a current density of 490 mA cm⁻² was achieved at 0.6 V in a single-cell level. Multi-heteroatom doping modulated the energy of OOH* and OH⁻ adsorption on the active sites, and the lowest overpotential (according to density functional theory calculations) was obtained for the Fe–Cu–N₃–C–P–S model.