Titanium-Decorated Planar Aluminene for Hydrogen Storage Using Density Functional Theory

Abstract

As green technology becomes a greater focus in our society, alternative energy like hydrogen fuel begins to have significance. Current technology has allowed the use of hydrogen as a fuel in fuel cells. However, a more efficient and safer means of storage would make hydrogen fuel more practical. Investigations on two-dimensional systems have already shown them to be potentially viable hydrogen storage devices. This study investigated one such 2-D system, a planar hexagonal aluminene decorated with titanium using density functional theory. Three possible adsorption sites for Ti atoms were chosen on aluminene: top, bridge, and hollow. This study showed that the Ti atom can be adsorbed at distances of 2.25 Å, 1.99 Å, and 0.00295 Å with binding energies of-2.356 eV, -4.219 eV, and-6.084 eV at the top, bridge, and hollow site, respectively. The density of states showed the Ti-decorated aluminene to be non-magnetic when the Ti atom was adsorbed at the top and bridge sites while adsorption at the hollow site resulted in a magnetic material. The charge density difference also showed chemisorption between the Ti and Al atoms which was consistent with the binding energies and the density of states. The hydrogen molecule was adsorbed on to the decoration at the top and hollow sites with binding energies of-1.41 eV and-0.494 eV, respectively. The H2 molecule dissociated at the top site with a dissociation barrier of 0.0266 eV and an imaginary frequency of 976.99 cm-1 in the vibrational spectrum. The results of the study showed that Ti-decorated aluminene can be a potential hydrogen storage material.