Unveiling the Catalytic Activity and Selectivity by Tuning the Coordination Environment of Cu Embedded on the WX ₂ (X═S, Se, and Te) Monolayer for the Nitric Oxide Reduction Reaction: Insights from the DFT Approach

In this work, the effect of the coordination environment in Cu embedded in an X-vacant WX₂ (X = S, Se, and Te) monolayer for the electrochemical NO reduction reaction (NORR) is investigated using the dispersion-corrected density functional theory (DFT-D3) approach. The stability of the Cu-WX₂ single-atom catalyst (SAC), NO adsorption configurations, and different reaction pathways for the electroreduction of NO to NH₃ are systematically examined. The catalytic activity and NH₃ selectivity are investigated at both low and high NO coverages by analyzing various descriptors such as the density of states, charge density difference, crystal orbital Hamilton population (COHP), and Gibbs free energy change. The major NORR competing with the hydrogen evolution reaction (HER) and also the byproducts like N₂O and N₂ formation are greatly suppressed by our Cu-WX₂ SACs. Among three different SACs, Cu-WTe₂ shows an excellent catalytic performance with the lowest limiting potential of -0.26 V, which follows the most favorable N-distal reductive pathway in their free energy profile. Overall, our results may pave the way for developing a single-atom catalyst under ambient conditions for ammonia synthesis and also offer directions for the rational design of a highly efficient NORR electrocatalyst.