Density functional theory investigation on hydrogen adsorption on buckled aluminene

Abstract

Hydrogen storage is one of the challenging components in hydrogen economy towards a cleaner energy. Two-dimensional materials are being explored as a potential hydrogen storage material. Adsorption of hydrogen on buckled aluminene was investigated using first principles with the incorporation of van der Waals correction via Tkatchenko-Scheffler method. Four possible adsorption sites were identified: top of the first layer, bridge, hollow, and top of the lowest layer. Critical results of energy calculations showed that hydrogen molecule can be physisorped on any sites of buckled aluminene with a binding energy of 0.77 eV without additional energy needed to store it. This physisorption is demonstrated in the density of states showing a slight broadening of energies. Hydrogen would prefer to be adsorbed as a molecule due to a dissociation barrier of 3.23 eV to recover the hydrogen. Another critical finding is that buckled aluminene has more possible hydrogen adsorption sites and higher binding energy than that of planar aluminene indicating a better candidate as a potential hydrogen storage material at a higher ambient temperature.