Molecular Hydrogen Storage in Stone–Wales Defected Single-Walled Carbon Nanotubes Using Molecular Dynamics Simulation

Abstract

The physisorption of molecular hydrogen (H₂) in Stone–Wales defected single-walled carbon nanotubes (D-SWCNTs) is investigated using molecular dynamics simulations (MDS). The interatomic and pairwise interactions between atoms and molecules are described by the AIREBO and Lennard–Jones (LJ) potentials. The effects of defect concentration, temperature, and pressure on hydrogen adsorption metrics have been thoroughly investigated. The findings reveal that (1) the existence of defective sites has a considerable impact on the gravimetric H₂ uptake of large-sized D-SWCNTs and (2) only a trivial difference in hydrogen adsorption is observed on increasing the defect concentration. However, the hydrogen storage capacity of D-SWCNTs exhibits a noticeable advantage over that of pristine SWCNTs as temperature decreases. The maximum H₂ uptake of D-SWCNTs is 9.11 and 1.33 wt% at 77 and 300 K, respectively. Besides, as compared to the requirement for reversible adsorption kinetics, the average binding energy of H₂ molecule in D-SWCNTs is quite low. The average binding energy ranges from 0.021 to 0.052 eV. While the adsorption capacity increases with increasing defect concentration, the mechanical stability of SWCNTs decreases, preventing the utilization of nanotubes for hydrogen storage with a higher defect concentration. We expect that the current studies will encourage researchers to put more effort into efficiently utilizing large-sized D-SWCNTs as a potential hydrogen storage medium.