Physical adsorption of hydrogen molecules on single-walled carbon nanotubes and carbon-boron-nitrogen heteronanotubes: A comparative DFT

Using dispersion-corrected density functional theory (DFT-D3) calculations, we study hydrogen adsorption on single-walled carbon (SWCNTs) and carbon-boron-nitrogen nanotubes (CBNNTs). Hydrogen adsorption energy (E-ad) values corresponding to the adsorption on the outer walls of SWCNTs and CBNNTs were calculated to be in the range from - 0.78 to - 0.81 and from - 0.92 to - 0.97 kcal/mol, respectively. The adsorption inside NTs exhibits enhanced E-ad: -4.03 (SWCNTs) and - 3.86 (CBNNTs) kcal/mol. The reduced density gradient (RDG) and independent gradient model (IGM) analyses exhibit dominating non-covalent interactions in all cases. The increase in H-2 coverages in the cases of both types of nanotubes does not lead to the sufficient E-ad decrease. The electronic properties of SWCNTs are independent of H-2 adsorption. Alternatively, these properties of CBNNTs are more sensitive to the H-2 addition, but the changes are rather minor. Our results show that CBNNTs are preferable to pure carbon counterparts for both hydrogen storage and sensing.