Transition metal atom doped C2N as catalyst for the oxygen reduction reaction: A density functional theory study

Abstract

The catalytic mechanism and activity of transition metal atom doped C2N (M-C2N, M = Fe, Co, Ni, and Cu) for the oxygen reduction reaction (ORR) are investigated in detail by density functional theory method. All the screened M-C2N are thermodynamically stable based on the binding energy calculations. The adsorption energy results indicate that the adsorption strength of O2 and ORR intermediates are decreased in the order of Fe-C2N ˃ Co-C2N ˃ Ni-C2N ˃ Cu-C2N, in which the adsorption energy values on Cu-C2N are most close to those on the Pt(111). Based on the relative energy diagram of ORR, the energetically favorable pathway on Fe-C2N and Co-C2N is direct 4e− mechanism, in which the O–O bond is directly dissociated after the second electron transfer. While for Ni-C2N and Cu-C2N, the most favorable pathway is indirect 4e− mechanism, in which the H2O2 is formed as the intermediate product. For all studied M-C2N, the Ni-C2N and Cu-C2N hold better catalytic activity, which could attribute to the contribution of metal atom and part of its activated nitrogen atoms.