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

Abstract

Metal-nitrogen-doped carbons (MNC) 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 NiNC 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 NiNC catalysts. These findings provide the modulation way and the underlying understanding of the reaction mechanisms for NiNC catalysts.