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

Abstract

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 (Ead) 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 Ead: -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 H2 coverages in the cases of both types of nanotubes does not lead to the sufficient Ead decrease. The electronic properties of SWCNTs are independent of H2 adsorption. Alternatively, these properties of CBNNTs are more sensitive to the H2 addition, but the changes are rather minor. Our results show that CBNNTs are preferable to pure carbon counterparts for both hydrogen storage and sensing.