Single Transition Metal Atoms Anchored on Defective MoS2 Monolayers 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 MoS2 catalysts decorated with transition metal atoms (TM@MoS2) is systematically studied. Sulfur defects innately generated during the preparation of MoS2 monolayers 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@MoS2 catalysts (TM = Ni, V, Cr, Nb, Ti) are found to be promising for affording NH3 with very low limiting potentials (U L = −0.18 to 0 V). Two TM@MoS2 catalysts (TM = Ag and Pt) are screened out for generating NH2OH, with U L of 0 V. The adsorption of NO is a good descriptor for eNORR’s activity and product selectivity. Thus, the TM@MoS2 catalysts may open a new avenue for electrochemical NH3/NH2OH synthesis and NO removal.