Mechanism Research Of Al₆X（X=Si,N,Cu）Clusters Hydrolysis Of Hydrogen Production And Hydrogen Storage

To build a renewable energy system is one of the most critical issues for the sustainable development of the mankind society and the natural environment. Hydrogen is considered as a clean alternative energy carrier because of its efficiency, abundance, and environmental friendliness. Hydrogen also causes no pollution and produces almost threefold the gravimetric heat of combustion of gasoline. The practical new energy source requires a renewable fuel to replace the traditional energy carrier. Hydrogen is definitely an ideal fuel for this goal. Therefore, effective methods of hydrogen generation and storage have attracted considerable attention.Firstly, we perform calculations to explore the mechanism for complete generation of the H₂ from a single H₂ O molecule. Based on density functional theory（DFT） calculations, we have found that two H atoms can be extracted from one H₂ O molecule in a three-step reaction by the catalysis of the Al₆ Si cluster. The reactant, product, and transition state（TS） are optimized and the reaction mechanism is analyzed. The reactions are closely related with the charge distribution of the Al₆ Si cluster. The dopant Si atom is responsible for the increase in the ability of the Al₆ Si cluster for capturing H₂ O before the reaction. The two reactions are supported by the wonderful charge distribution. The present findings provide a new concept for the complete extraction of H₂ from H₂ O molecule, which is a promising method for hydrogen production.In order to find more hydrolysis hydrogen production material, we investigate the adsorption and dissociation of H₂ O molecule on Al₆ Cu cluster. Results show that the reaction is endothermic reaction. The dopant Cu atom is responsible for the increase of the ability of the Al₆ Cu cluster to capture H₂ O before reaction and the suitable charge distribution to support the two reactions. The present findings provide a new insight into the release of H₂ from H₂ O molecule via catalysis with Al₆ Cu cluster, which is a promising way to produce hydrogen.Secondly, the adsorption and dissociation of H₂ on cluster Al₆ Si are investigated based on the density functional theory with the generalized gradient approximation. The stable geometrical structures of reactants and products, the transition states, and the reaction paths for the dissociation are investigated. We also obtained the energy barrier. In the same way, we study adsorption and dissociation of H₂ on Al₆ N. The results show that the adsorption energies of H2@ Al₆N are small, which implies they are not suitable for storing H₂ directly. However, the energy barrier for each reaction is found in the range of 0.6226¹.1256 eV, implicating that Al₆ N can store hydrogen with dissociating the H₂ into separate atoms under appropriate conditions.Finally, we investigate the adsorption of CO molecule on Al₆ Si cluster to explore more applications of the doped Al cluster. Based on hybrid DFT calculations, the geometrical structures of CO on Al₆ Si cluster are optimized and analyzed by adsorption energy（Ea）. In order to examine the thermal stability of the adsorbed complexes（CO）₆@ Al₆Si, we carried out molecular dynamics simulations using the atom centered density matrix propagation molecular dynamics model at the temperature of 373 K. The results show that four or more CO molecules can remain in the Al₆ Si cluster at the temperature after 1ps（10000 time steps）. It implies that Al₆ Si cluster is a high efficient carrier to adsorb CO molecules.