Modulating local coordination of Ni-Nx-C electrocatalysts for improving oxygen reduction activity by the first-principles calculations

Metal-nitrogen-doped carbons (M-N-C) are regarded as a type of promising electrocatalysts for oxygen reduction reaction (ORR) due to their low cost and high activity. Here we introduce a series of heteroatoms (Si, P, S, As, Se, Br, Te, I) in Ni-N-C to modulate the local coordination of Ni for improving the ORR catalytic activity based on the density functional theory calculations. The results reveal that NiN3S-C and NiN2PC-C exhibit not only low overpotentials based on the increased charge density of Ni site but also high stability. Moreover, the results from different reaction pathways show that the OOH* -> OH*+OH* step exhibits the lower activation energies than those of OOH*-> O*. Besides, the HOOH* formation from OOH* has a lower activation energy than OOH*-> O* step, suggesting the possible generation of H2O2 in Ni-N-C catalysts. These findings provide the modulation way and the underlying understanding of the reaction mechanisms for Ni-N-C catalysts.