First-Principles Study Of Nano Materials For Hydrogen Storage

Hydrogen is a new clean energy carrier as its rich resources, renewable and high thermal efficiency. The biggest challenge to hydrogen economy is how to storage hydrogen safely, effectively and economically. Conventional methods of hydrogen storage as gas, liquid or solid state are not the ideal way cause of theirs malpractice. At present, extensive research in the hydrogen storage material such as carbon-based nano material, metal hydride, MOFs structures and organic hydrogen storage material. Although some studies suggest that some hydrogen storage material have density of hydrogen storage, but as a application of which still have problems. The aluminum cluster as a hydrogen storage material studied by this paper is different from aluminum hydride which adsorb hydrogen by the chemical adsorption, while aluminum cluster adsorb hydrogen under the charge polarization mechanism.Our first principle calculation is carry out by the density function theory (DFT). The AljoLig cluster is a magic cluster recognized by Kumar. First of all, we studied the structure stability of the D5h structure, and then its hydrogen storage capacity and hydrogen mechanism. We found that the D5h AlioLi8cluster has a large band gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) and together with covalent bonding. These two factors determine D5h structure of AlioLi8the most stability. The Li atom gets a net charge of0.84e, which enhance the adsorption of hydrogen. The study shows that the maximum hydrogen storage gravimetric densities for cluster is10.4wt%ith binding energy of77meV/H2.The Al30Li32cluster compound by Al10Li8was considered by us. The storage capacity approaching7.2wt%and then the binding energy reaching80meV/H2. For the much longer assembled tubular material, the maximum hydrogen storage capacity would be reaching7.2wt%, and then the binding energy would be reaching80meV/H2. Thus such nano material could be the ideal hydrogen storage media for the application. We used first-principles study the strain effect on the adsorption of H2on transition metal phthalocyanine sheet. It’s interesting to find that, for3d and4d TMPc, the external stretch could enhance the adsorption of hydrogen. The more stretcher of TMPc, the bigger of the bind energy, so as the H-H bond and the distance of TM and H2. We still find that the compressed TMPc sheet have the lower binding energy of H2. The mechanism of TMPc adsorbs H2follow the Kubas mechanism. The maximum gravimetric densities of3d TMPc could reach1wt%. On the one hand, the hydrogen molecules can only be adsorbed on the transition atom, on the anther hand, when one more hydrogen molecule is added; there is a repulsion force between two molecules. Thus affect the total number of hydrogen uptake. The study showed that compression could reduce the adsorption between TMPc and hydrogen molecules thus achieve the adsorption and desorption of the hydrogen.