A First Principle Study to Understand the Importance of Edge-exposed and Basal Plane Defective MoS Towards Nitrogen Reduction Reaction.

Nitrogen reduction reaction (NRR) as a promising approach to ammonia synthesis has received much attention in recent years. Molybdenum disulfides (MoS), as one of the most potential candidates for NRR, are extensively investigated. However, the inert basal plane limits the application of MoS. Herein, by using density functional theory (DFT) calculations, we constructed edge-exposed MoS and different kinds of basal plane defects, including anti-site, sulfur vacancy and pore defects, to systematically investigate their influence on the NRR performance. The thermodynamically calculated results revealed that the NRR on edge-exposed MoS, anti-site defects, sulfur vacancy with three sulfur atoms missing (S) and porous defect (D) exhibit great catalytic activity with low limiting potentials. The calculated limiting potentials are -0.43 and -0.47 V at armchair and zigzag edge MoS, -0.42 and -0.44 V at anti-site defects, -0.49 and -0.67 V at S and D. However, by inspecting the thermodynamic properties of the hydrogen evolution reaction, we proposed that the zigzag-end MoS and anti-site defects exhibit a better NRR selectivity compared to armchair-end MoS, S and D. Electronic structure calculations reveals that the edge-exposed and basal plane defective MoS can improve the conductivity of the material by reducing the band gap. Donation-backdonation mechanism can effectively promote the activation of nitrogen molecule. Our results pave the way to understanding the defective effects of the MoS inertness plane for NRR and designing high-performance NRR catalysts.