Single Transition Metal Atoms Anchored on Defective MoS₂Monolayers for the Electrocatalytic Reduction of Nitric Oxide into Ammonia and Hydroxylamine

Ammonia (NH₃) and hydroxylamine (NH₂OH) are important feedstocks in the chemical industry. Electrocatalytic reduction of nitric oxide (eNORR) to these chemical feedstocks is desirable for green energy conversion and waste utilization. In this work, by means of density functional theory (DFT) calculations, the eNORR activity of defective single-layer MoS₂catalysts decorated with transition metal atoms (TM@MoS₂) is systematically studied. Sulfur defects innately generated during the preparation of MoS₂monolayers are natural hosting sites for TM atoms. Out of the 27 considered TM@MoS₂(3d to 5d period) catalysts, 19 are thermodynamically stable and experimentally feasible. Among these 19 candidates, 13 exhibit a high eNORR activity toward NH₃, while six prefer the production of NH₂OH. Then, their abilities to inhibit hydrogen evolution reaction (HER) and byproducts (N₂O/N₂) are evaluated. Eventually, five TM@MoS₂catalysts (TM = Ni, V, Cr, Nb, Ti) are found to be promising for affording NH₃with very low limiting potentials (U_L= -0.18 to 0 V). Two TM@MoS₂catalysts (TM = Ag and Pt) are screened out for generating NH₂OH, with U_Lof 0 V. The adsorption of NO is a good descriptor for eNORR's activity and product selectivity. Thus, the TM@MoS₂catalysts may open a new avenue for electrochemical NH₃/NH₂OH synthesis and NO removal.