Defected MoS2: An efficient electrochemical nitrogen reduction catalyst under mild conditions

Although the electrochemical N 2 reduction reaction (NRR) to NH 3 provides a promising avenue for artificial N 2 fixation, building of efficient NRR electrocatalysts with high activity and stability remains a tremendous challenge. The combined experimental results and theoretical calculation reveal that MoS 2 with sulfur-vacancy defect (V S -MoS 2 ) is an admirable NRR catalyst. Electrochemical results demonstrate that V S -MoS 2 (5:2) possesses outstanding NRR performances, including a superior NH 3 average yield rate (46.1 × 10 −11 mol s −1 cm −2 at -0.5 V vs reversible hydrogen electrode (RHE)), an excellent faraday efficiency (FE: 4.58% at -0.4 V vs RHE), good electrochemical stability (at least 24 h), and high selectivity (no by-product of N 2 H 4 ). Density functional theory (DFT) calculations demonstrate that the rate determining steps (RDSs) of all V S -MoS 2 (010)-2, V S -MoS 2 (010)-1, and MoS 2 (010) are the first hydrogenation step to form *NNH intermediate, as reflected by the energy barriers of 0.06 eV, 0.20 eV, and 0.93 eV, the significantly charge transfer (1.02 e , 0.45 e vs. 0.41 e ) from two Mo atoms to N 2 , as well as the stretching of N N bond (1.200 Å, 1.140 Å vs. 0.970 Å), respectively. These results reveal that V S -MoS 2 (010)-2 can effectively activate inert N 2 molecule and have the potential application in nitrogen fixation under mild conditions.