Tetrahedral silsesquioxane-C₂H₂Ti complex for hydrogen storage

The interaction of molecular hydrogen with tetrahedral silsesquioxane (T₄)-C₂H₂Ti complex has been studied using Density Functional Theory with M06-2X functional and MP2 method with 6-311++G** basis set. T₄-C₂H₂Ti complex can absorb maximum five hydrogen molecules with the gravimetric hydrogen storage capacity of 3.4 wt %. Adsorption energy calculations show that H₂ adsorption on T₄-C₂H₂Ti complex is favorable at room temperature by both the methods. We have studied the effect of temperature and pressure on Gibbs free energy corrected adsorption energies. Molecular dynamics simulations for H₂ adsorbed T₄-C₂H₂Ti complex have also been performed at 300K and show that loosely bonded H₂ molecule flies away within 1fs. Various interaction energies within the complex are studied. Stability of a complex is predicted by means of a gap between Highest Occupied Molecular Orbital (HUMO) and Lowest Unoccupied Molecular Orbital (LUMO). The H₂ desorption temperature for T₄-C₂H₂Ti complex is calculated with Van’t Hoff equation and it is found to be 229K.