Hydrogen Desorption from Ti-Doped MgH₂(110) Surfaces: Catalytic Effect on Reaction Pathways and Kinetic Barriers

Transition-metal (TM) catalytic dopants are widely used in hydrogen-storage materials to increase hydrogen (H 2 ) desorption and absorption kinetics. Using density functional theory calculations, we elucidate the catalytic effect of Ti substitutional dopant on H 2 desorption from MgH 2 (110) surfaces. Kinetic energy barriers of H 2 desorption pathways are calculated via a nudged-elastic-band method. For a Ti-doped surface, we identify a concerted mechanism involving H bulk (vacancy-mediated) diffusion to feed H 2 surface desorption, arising from a synchronized diffusion of H atoms around Ti. The kinetic barrier for the Ti-doped surface is reduced by 0.41 eV—a 22% drop. We also show that the catalyzed H 2 desorption is mediated by a change in hydrogen coordination number of Ti, altering the associated Ti spin state.