期刊
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
卷 34, 期 4, 页码 1922-1930出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijhydene.2008.11.109
关键词
Metal hydrides; Hydrogen absorption; First principles calculations
资金
- EPSRC
- Engineering and Physical Sciences Research Council [EP/C546385/1] Funding Source: researchfish
- EPSRC [EP/C546385/1] Funding Source: UKRI
The kinetics of hydrogen absorption by magnesium bulk is affected by two main activated processes: the dissociation of the H-2 molecule and the diffusion of atomic H into the bulk. In order to have fast absorption kinetics both activated processed need to have a low barrier. Here we report a systematic ab initio density functional theory investigation of H-2 dissociation and subsequent atomic H diffusion on TM (= Ti, V, Zr, Fe, Ru, Co, Rh, Ni, Pd, Cu, Ag)-doped Mg(0001) surfaces. The calculations show that doping the surface with TMs on the left of the periodic table eliminates the barrier for the dissociation of the molecule, but the H atoms bind very strongly to the TM, therefore hindering diffusion. Conversely, TMs on the right of the periodic table do not bind H, however, they do not reduce the barrier to dissociate H-2 significantly. our results show that Fe, Ni and Rh, and to some extent Co and Pd, are all exceptions, combining low activation barriers for both processes, with Ni being the best possible choice. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
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