Progressive Dehydrogenation of LiNH₂ Materials on Ru(0001) Based on ab initio Interface Models

Density Functional Theory calculations were performed to design atomistic models of ruthenium surfaces interfaced with partially dehydrogenated lithium-based layers (LiNH₂, Li₂NH, and Li₃N). The structural, energetic, and magnetic properties of Li₂NH and Li₃N bulks and surfaces were systematically evaluated by using the GGA-PBE and dispersion-corrected PBE-dDsC functionals. The surface-termination analysis showed that the (100) orientations of these compounds minimize the lattice mismatch with Ru(0001), favoring interface formation. Based on these results, a multilayer model, Ru(0001)/Li₃N(001)/Li₂NH(001)/LiNH₂(001), was developed to describe the progressive dehydrogenation of LiNH₂ in contact with Ru. The partially dehydrogenated interface showed a greater thermodynamic stability than fully hydrogenated systems. Energetic and magnetic analyses indicated that progressive dehydrogenation enhances interfacial stability, allowing the suggestion of mechanistic assumptions for ammonia decomposition. Overall, this study offers an atomistic perspective on Li-N-H/Ru interfaces and a basis for designing improved catalysts for ammonia decomposition and hydrogen storage.