Enhancement in the hydrogen storage capability of borophene through yttrium doping: A theoretical study

In this study, we conducted first-principles density functional calculations to investigate the effect of Yttrium (Y) doping on β₁₂-Borophene for hydrogen storage. The negative adsorption energy results proved that hydrogen molecules adsorption on Y-doped β₁₂-Borophene (Y@Borophene) monolayer is exothermic and thermodynamically stable. The obtained adsorption energy results proved that the doped Y atoms attached strongly on β₁₂-Borophene surface and don't tend to form a metal cluster. Moreover, results indicate that Y@Borophene can bind up to six hydrogen molecules with an average adsorption energy of −0.141 eV/H₂. The adsorption energy results between Y@Borophene complex and hydrogen molecules ranged from −0.133 eV to −0.178 eV which is an acceptable range for an ideal H₂ storage material. The Y@Borophene can lead the hydrogen gravimetric density to exceed the 5.5 wt% target of US Department of Energy. Moreover, the obtained electronic properties exhibit the charge transfer which occurred from the Y atom to boron atoms of borophene and from hydrogens to Y atom. The projected density of states (PDOS) analysis verifies the orbital hybridisation which primarily occurs between B-p, H-s, and Y-d orbitals, indicating the potential of hydrogen adsorption capability. Molecular dynamic simulation results confirmed that the desorption temperature range of Y@Borophene is between 186 and 334 K and had a great H₂ desorption performance in the ambient temperature that is ideal for vehicle fuel cell operation. Therefore, this theoretical study presents the Y@Borophene is a prospective material for hydrogen storage system.