Strain-engineered molybdenum Diboride and tungsten Diboride monolayers as efficient catalysts for sustainable ammonia...

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 (MoB₂) and Tungsten Diboride (WB₂) 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 MoB₂ and WB₂ 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_diss). During NO reduction to NH₃, 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 MoB₂ and WB₂ 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 MoB₂ and WB₂ monolayers as promising candidates for efficient and selective NORR catalysts, providing a viable pathway for sustainable NH₃ synthesis.