First principles study of hydrogen storage on B-doped SiC monolayers through light transition metal atoms

In this first-principles study, based on Density Functional Theory, we assess the capacity of metal-decorated, boron-doped, graphene-like monolayers of silicon carbide (SiC) to adsorb hydrogen molecules. To enhance the binding of metal adatoms on SiC monolayers, these were substitutionally doped with boron atoms. Alkaline, alkaline-earth, and transition metal adatoms were considered and their hydrogen storage capabilities were compared. The results show that alkaline-earth metal adatoms are not suitable for hydrogen storage. On the other hand, sodium- and potassium-decorated B-doped SiC monolayers adsorb the largest number of H2 molecules per adatom, but their adsorption energies are insufficient for an adequate hydrogen storage. Titanium and scandium adatoms are the most suitable for hydrogen storage since they exhibit good adsorption energies and up to four and five H2 molecules per adatom, respectively. Moreover, the estimated potential barriers for diffusion of these two adatoms on the B-doped SiC monolayers indicate that the probability of clustering is very low. Moreover, within the ideal-gas approximation, it is estimated that hydrogen can be stored in the Ti- and Sc-decorated monolayers at room temperature and atmospheric pressure. Furthermore, if SiC monolayers were doped with boron atoms in concentrations similar to those reported for graphene, it is estimated that the gravimetric capacities could reach 5.1 wt% and 6.3 wt% for Ti-decorated and Sc-decorated monolayers, respectively, which are close to the target hydrogen-storage capacities envisioned for the near future.