Quantum computational chemical calculations to estimate the necessary energy for hydrogen storage in the metal hydrides AlH3ScH3 and Al2H6

Abstract

Hydrogen storage describes the methods of storing H2 for subsequent use. Hydrogen storage is the main issue that needs to be solved before the technology can be implemented into key areas such as transport. The high energy density, good stability and reversibility of metal hydrides make them appealing as hydrogen storage materials. Metal hydrides have the potential for reversible on‐board hydrogen storage and release at low temperatures and pressures. The aim of this thesis is to describe, document and carry out the previous theoretical quantum chemical calculations by density functional theory (DFT) at B3LYP level of theory with 6‐311++G(3df,3pd) basis set for aluminium and hydrogen, and a SDD pseudopotential for scandium in order to; first of all, optimize the molecular structures; secondly, predict the vibrational frequencies of the optimized structures and finally estimate the energies needed to absorb and release hydrogen from both metal hydrides AlH3ScH3 and Al2H6. Our calculated results show that the hydrogen absorption energy value for the formation of AlH3ScH3 (‐47,479kcal/mol) is higher than the value for the formation of Al2H6 (‐33,481 kcal/mol). These were not the expected results because the energy has been increased, and thus the operation temperatures are also higher. The transition metal scandium in the hydride does not decrease the hydrogenation energy due to cation matrix that seems to be the responsible for the thermal stability.