Effects of Li on hydrogen absorption properties of Mg_(17)Al_(12)(110) surface: A density functional theory study

摘要

On the basis of density functional theory (DFT), the catalytic effects of Li on hydrogen absorption properties of the Mg17Al12(110) surfaces are studied. The Li-containing Mg17Al12(110) surfaces were composed of the Li-substituted and Li-adsorbed systems, namely Mg17Al12(110) and Mg17Al12(110)/Li surfaces, respectively. Calculations indicate that adsorption energies of H (H-2) on the Mg17Al12(110) surfaces with a low amount of Li were significantly improved relative to hydrogen on the clean surface. Especially, the energy of H (H-2) on the Mg17Al12(110)/Li system was -0.68 (-0.48) eV. Moreover, the addition of Li remarkably promotes the dissociative properties of H-2 on the (110) surface. The barrier energy of H-2 dissociation on the Mg17Al12(110)/Li surface was 0.14 eV, which was much lower than that (0.87 eV) on the pure surface. Analysis of electronic structures reveals that the H-s orbital hybridized with the Mg-s evidently in the Li-containing systems. The formation of Li-H bond and the interaction between H-2 and Li atom may explain the enhanced hydrogenation properties of Mg17Al12(110)/Li surface. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.