Secondary doping of Mn/Co bimetallic ZIF-derived catalysts for the oxygen reduction reaction

Abstract

The development of a low-cost oxygen reduction reaction (ORR) catalyst with high activity and durability is important. Here, we report a bimetallic catalyst based on a secondary doping approach to the preparation of a Mn, Co, and N co-doped carbon (Mn_0.1Co_0.3/NC-2) catalyst. Secondary doping increases the number of M–N_x (M = Mn, Co) active sites in the Mn_0.1Co_0.3/NC-2 catalyst. In addition, the doping of Mn improves the graphitization degree of the carbon substrate, thereby increasing the corrosion resistance and catalytic durability of the catalyst; the doping of Co nanoparticles improves the pore structure of the catalyst, thereby increasing the accessibility of the active sites and the mass transfer efficiency of the ORR. The catalysts exhibit an excellent ORR performance due to the increased number of M–N_x active sites by secondary doping and the synergistic effect of the Mn and Co bimetals. In alkaline media (0.1 M KOH), the half-wave potential (E_1/2) of Mn_0.1Co_0.3/NC-2 (0.903 V) is 44 mV higher than that of Pt/C (0.859 V), and E_1/2 decays only by 10 mV after 5000 cycles. In acidic media (0.1 HClO₄) it also shows a superior ORR performance with an E_1/2 of 0.812 V.