Strain-engineered molybdenum Diboride and tungsten Diboride monolayers as efficient catalysts for sustainable ammonia production via nitric oxide reduction.

Electrocatalytic nitric oxide reduction reaction (NORR) is a promising alternative to achieve ecofriendly ammonia synthesis and maintain the global N balance. In this study, the catalytic performance of Molybdenum Diboride (MoB) and Tungsten Diboride (WB) monolayers for NORR was investigated using density functional theory (DFT) calculations. The catalytic activity and selectivity of B-surfaces and transition metal (TM)-surfaces were comprehensively investigated. The thermodynamic stability of MoB and WB monolayers was confirmed through cohesive energy calculations, ab initio molecular dynamics simulations (AIMD), and phonon spectra analysis. Additionally, the electrochemical stability was evaluated using dissolution potential (U). During NO reduction to NH, the directional charge transfer from the TM surface to the B surface improves the problem of insufficient p electrons in the B atom itself and optimizes the adsorption energy of NO. Compared to other MBenes, the B-surfaces of MoB and WB exhibited significantly enhanced catalytic performance on their B-surfaces, with lower limiting potentials of -0.16 V and - 0.08 V, respectively. Subsequently, we further elaborated the mechanism of NO molecule activation through the "donation/anti-donation" mechanism of σ → px/py and pz → π*. Furthermore, the effects of biaxial tensile strain (-2 % to 2 %) on the electronic structures, activity trends, adsorption behaviors, and underlying mechanisms of these monolayers were systematically explored. The findings underscore MoB and WB monolayers as promising candidates for efficient and selective NORR catalysts, providing a viable pathway for sustainable NH synthesis.