Hydrogen adsorption on Ce/BNNT systems: A DFT study

The adsorption of H₂ on Ce-doped boron nitride nanotubes (BNNT) is investigated by using density functional theory. For the Ce/BNNT system, it is found that Ce preferentially occupies the hollow site over the BN hexagon. The results indicate that seven H₂ per Ce can be adsorbed and 5.68 wt% H₂ can be stored in Ce₃/BNNT system. Among nanotubes doped with metals, Ce exhibits the most favorable hydrogen adsorption characteristics in terms of the adsorption energy and the uptake capacity. Both hybridization of the Ce-5d orbital with the H-1s orbital and the polarization of the H₂ molecules contribute to the hydrogen adsorption. Ce clustering can be suppressed by preferential binding of Ce atoms on BNNT, which denotes that BNNT as a hydrogen storage substrate is better than CNT due to its heteropolar binding nature.