A First Principle Study to Understand the Importance of Edge-exposed and Basal Plane Defective MoS2 Towards Nitrogen Reduction Reaction.

Abstract

Nitrogen reduction reaction (NRR) as a promising approach to ammonia synthesis has received much attention in recent years. Molybdenum disulfides (MoS₂), as one of the most potential candidates for NRR, are extensively investigated. However, the inert basal plane limits the application of MoS₂. Herein, by using density functional theory (DFT) calculations, we constructed edge-exposed MoS₂ 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 MoS₂, anti-site defects, sulfur vacancy with three sulfur atoms missing (S_3V) 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 MoS₂, -0.42 and -0.44 V at anti-site defects, -0.49 and -0.67 V at S_3V and D. However, by inspecting the thermodynamic properties of the hydrogen evolution reaction, we proposed that the zigzag-end MoS₂ and anti-site defects exhibit a better NRR selectivity compared to armchair-end MoS₂, S_3V and D. Electronic structure calculations reveals that the edge-exposed and basal plane defective MoS₂ 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 MoS₂ inertness plane for NRR and designing high-performance NRR catalysts.