Electronic properties and hydrogen storage capacity of the α-Ge nanostructures

The stability and electronic properties of αGe nanocrystals and nanoflakes were studied in the [111] and [110] crystallography directions. The findings showed that the electronic properties of the αGe flakes depend on crystallographic directions, shape, and system size, with well-behaved trends observed as the structure grows. It is demonstrated that the 111-αGe systems can store one hydrogen molecule per Ge-ring on their surface, with significantly improved capacity when considering the adsorption of Nb atoms on the αGe surface. The Nb@αGe system can store at least three H2 molecules per Nb atom, with an estimated hydrogen weight percent of 6.11%. An applied strain of about 1% decreased the binding energy by ∼20%, indicating that strain can be an important alternative for engineering the bond between H2 and the Nb@αGe surface. Based on these findings, the αGe surface is identified as a promising material for hydrogen storage, particularly with Nb atoms adsorbed on its surface, paving the way for further studies on the practical applications of 2D-α-Ge in this field.