Adsorption And Dissociation Of H₂on Aluminum Cluster Anions Studied By Ab Initio Calculations

Increasing concerns over future energy resources, global production of carbon dioxideand impacts of global warming are driving society to search for a replacement for fossil fuelsand to improve clean energy technologies. Hydrogen is the ideal candidate as an energycarrier for some advantages such as clean, high efficiency, safety, renewable; and it can avoidadverse effects to the environment. And reducing depends on imported oil for countrieswithout natural resources. Hydrogen is praised as the green energy of the21st century, whichplays an important role in the new energy research of the future. Nowadays the most difficultyis the hydrogen energy storage in the large-scale usage of hydrogen. Therefore, looking for anideal hydrogen storage material has become a research hot issue. At present, There is no onekind of material can meet the high storage density, the good thermodynamics and kinetics ofstore performance simultaneously. It is significant to look for one kind of high-performancehydrogen storage materials through investigating the interaction of the H₂molecules and thematerial and the mechanism of dissociation.Applying accurate ab initio methods, the adsorption and dissociation process of H₂molecule on Al₇^-and Al₈^-cluster anion is investigated. First all kinds of the structures of Al₇^-and Al₈^-cluster anion are fully optimized. And then the structure with the lowest energy isselected for the adsorption. The structures of the H₂molecule adsorbed on the surface of Al₇^-and Al₈^-cluster anion are optimized without any restrict, and the dissociation process of H₂molecule on Al₇^-cluster anion is investigated in detail. Finally, we analyze the density ofstates of the structures and compare with those obtained by the photoelectron spectroscopy.The calculations indicate that the adsorption of H₂on Al₇^-and Al₈^-is weak physicaladsorption with the adsorption energy about0.02eV and0.01eV, respectively. By means ofcalculation, that the structure of Al₇^-cluster anion is unique using the different method and thedissociation process shows that the energy barrier of dissociation is about0.75eV. The densities ofstates of the Al₇^-and Al₈^-cluster and the dissociative adsorption complex Al7H₂-are in goodagreement with the photoelectron spectroscopy observed. It determines that the dissociativeadsorption of H₂on Al₇^-can be observed by experiment.