N2 reduction using single transition-metal atom supported on defective WS2 monolayer as promising catalysts: A DFT study

Abstract

Nitrogen reduction reactions (NRRs) under mild conditions retain an enormous challenge in effective N 2 activation on metal-based catalysts. Here, by spin-polarized DFT calculations, we systematically investigated the potential of single transition-metal atoms (Sc to Zn, Nb to Cd, W, Pt and Au) supported on the experimentally available WS 2 nanosheets with sulfur vacancies as catalysts for N 2 fixation and conversion. The results confirm that the WS 2 nanosheet with sulfur vacancies is a good platform for anchoring single transition-metal atoms. Based on proposed several criteria, it is found that the single Ni atoms anchored to sulfur vacancies possess outstanding catalytic activity of NRR. Here, the Ni-WS 2 nanosheet acts as likely Lewis-acid system and accepts electrons from the N 2 *, which causes the weakening of N–N bond. Reaction energy diagrams of the NRRs show that the whole NRRs on Ni-WS 2 surface prefer to occur along the alternating associative pathway, and form the ammonia without the requirement of energy input. Overall, our results reveal that the Ni-WS 2 system is a quite promising single-atom catalyst with less energy-consuming and good stability for NRRs. These findings could motivate more experimental and theoretical researches to further explore the potential of single transition-metal atoms anchored to two-dimensional substrate materials for NRRs. • WS 2 nanosheet with S-vacancies is potential substrate for anchoring single TM atoms. • Single Ni atom anchored to the S-vacancy possesses outstanding NRR catalytic activity. • Stability of reaction intermediate relates to the charge difference between two nitrogen atoms. • NRR on Ni-WS 2 surface prefers to occur along the alternating associative pathway. • Ammonia can form on the Ni atom without the requirement of energy input.