First principles investigation on the hydrogen adsorption on planar aluminene with boron, carbon, and nitrogen as impurities

Materials including two-dimensional systems have been widely investigated for potential hydrogen storage. In this work, hydrogen adsorption on planar hexagonal aluminene with boron, carbon, and nitrogen decorations was studied using density functional theory. Results showed that boron, carbon, and nitrogen atom can be chemisorped without barriers on aluminene sites: top, hollow, and bridge. Density of states (DOS) showed that these systems remained metallic and nonmagnetic except for adatoms on top site of aluminene but its ferromagnetism are passivated once hydrogen atoms are adsorbed. The <i>p</i> orbitals of the adatoms and aluminium atoms formed the chemical bonding as shown by the DOS and supported by the charge density difference. Potential energy barriers were found in hydrogen adsorption on all systems indicating additional energy is needed to adsorb hydrogen on all systems. Hydrogen is chemisorped on surfaces where adatoms are at the top and bridge site through its <i>s</i> orbital and <i>p</i> orbital of the adatom, while H₂ is physisorped for adatoms on the hollow site. The presence of boron, carbon, and nitrogen atoms on aluminene can reduce the hydrogen capacity of pristine aluminene due to the potential energy barriers.