Selective hydrogen molecule dissociation on Ca2N monolayer

Abstract

The development of efficient hydrogen conversion and storage technologies is critical for sustainable energy systems. We report the remarkable discovery of barrierless hydrogen dissociation on dicalcium nitride (Ca₂N) monolayers through density functional theory calculations and ab initio molecular dynamics simulations. Our investigations reveal that molecular hydrogen adsorption occurs exclusively at a bridge site between calcium atoms (site B), while dissociated hydrogen atoms preferentially migrate to a calcium-centered hollow site (site A). Importantly, our simulations demonstrate a self-regulating mechanism wherein initial H₂ dissociation at B-sites inhibits subsequent molecular hydrogen adsorption, effectively controlling the dissociation process. The absence of an activation energy barrier indicates an exceptionally favorable thermodynamic pathway for hydrogen dissociation under ambient conditions. These findings establish pristine Ca₂N monolayers as promising candidates for catalyzing hydrogen evolution reactions and other hydrogen-related energy applications, offering a novel direction for the development of electride-based catalysts with unprecedented hydrogen activation properties.