Investigation of hydrogen storage capabilities related properties of various nano-materials by using computational chemistry methods

In this thesis, hydrogen storage and related properties of nanostructures such as Boron Nitride (BN), Aluminum Nitride (AlN) and Silicon Carbide (SiC) were investigated by using computational chemistry methods. In the structures of the BN, AlN and SiC nanosheets, there are areas that most interact with the hydrogen molecule. These areas can be defined as safe zones for the hydrogen molecule. According to the safe zones, hydrogen storage properties of nanosheet structures have been determined. According to the calculations, the SiC nanosheet molecule is a better hydrogen storage medium than the other nanosheet. In addition, the best density functional theory (DFT) and the semi-empiric method were determined for the BN and AlN nanocage systems having weak non-covalent interactions according to the CCSD(T) reference method. Among the DFT methods and semi-empiric methods used, the DFT-ωB97X-D and PM6-DH2 methods were the best method for those systems. In addition, the PM6-DH2 method gives good results as well as the DFT-ωB97X-D method and it is more suitable in terms of computing time according to DFT-ωB97X-D method. In addition, for those nanocage structures, it has been investigated whether the hydrogen molecule can be stored as endohedral or exohedral form. According to the calculations, hydrogen cannot be stored in the BN nanocage structure while the hydrogen molecule can be stored in the AlN nanocage structure. The reason of this is that the hydrogen molecule breaks the B-N bond as it passes through the BN nanocage. In other words, the BN nanocage structure can store hydrogen molecule as exohedral form. By the addition of hydrogen molecule, the structure of AlN nanocage is more stable than the structure of BN nanocage. Therefore, the AlN nanocage structure is a better hydrogen storage material than the BN nanocage structure.