Metal (metal = Fe, Co), N codoped nanoporous carbon for efficient electrochemical oxygen reduction

Metal, N codoped nanoporous carbon (N-M-nC, M - Fe, Co) is prepared by in situ incorporation of the metal during the formation of the nanoporous carbon skeleton followed by NH3 treatment. The samples exhibit superior catalytic performance for the oxygen reduction reaction (ORR) in alkaline electrolytes. M, N codoping shows a synergic effect with improved ORR performance compared to the sample with only nitrogen dopant (N-nC), in the order of N-Fe-nC > N-Co-nC > N-nC, indicating that the M-N synergic effect is critical for high ORR performance in alkaline electrolyte. A detailed structural characterization of the catalysts is carried out, which suggests that the improved ORR performance should be attributed to the formation of active sites with M-N bonding. Other structural differences, including surface area, porosity and carbon structure, play a minor role. The performance of the N-Fe-nC sample is comparable to that of commercial Pt/C, including more positive onset and halfwave potential, comparable saturation current density and a dominant four-electron pathway, which suggests that nanoporous carbon can serve as an ideal platform for developing high performance ORR catalysts via proper doping.