科研之友
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摘要
Hydrogen is considered as a potentially ideal substitution for fossil fuels in the future sustainable energy system because it is an abundant, clean and renewable energy carrier. A safe, efficient and economic storage method is the crucial prerequistite and the biggest challenge for the wide scale use of hydrogen. The nanomaterial is one of the most promising hydrogen storage materials because of its high surface to volume ratio, unique electronic structure and novel chemical and physical properties. It has been demonstrated that pristine nanostructures are not suitable for hydrogen storage, since they interact weakly with hydrogen molecule and their hydrogen storage density is very low. However, the hydrogen storage capacity of the nanostructures can be significantly enhanced through substitutional doping or decoration by metal atoms. Using density functional theory, we investigate the properties of hydrogen adsorption on Li-decorated C-24 clusters. Results show that the preferred binding site for Li atom is the pentagonal rings. The interaction of Li atoms with the clusters is stronger than that among Li atoms, thus hindering effectively aggregation of Li atoms on the surface of the cluster. The decorated Li atoms are positively charged due to electron transfer from Li to C atoms. When H-2 molecules approach Li atoms, they are moderately polarized under the electric field, and adsorbed around the Li atoms in molecular form. Each Li atom in the Li-decorated C-24 complexes can adsorb two to three H-2 molecules. The H-H bond lengths of the adsorbed H-2 molecules are slightly stretched. The average adsorption energies are in the range of 0.08 to 0.13 eV/H-2, which are intermediate between physisorption and chemisorption. C24Li6 can hold up to 12 H-2 molecules, corresponding to a hydrogen uptake density of 6.8 wt%. This value exceeds the 2020 hydrogen storage target of 5.5 wt% proposed by the U. S. Department of Energy.
- 出版日期2015-12-5
- 单位西北师范大学
