Study on hydrogen uptake of CSCNTs with different etching degrees and apex angles by the GCMC simulation

In this study, the hydrogen uptakes of the cup-stacked carbon nanotubes (CSCNTs) with different etching degrees and apex angles at 298 K and 1–10 MPa are investigated by the Grand Canonical Monte Carlo simulation. The simulated results show that the single-layer etching can increase the total specific surface area of CSCNTs, at the same time, enhance the C-H interaction by forming micropores with overlap potential field for hydrogen molecules. Under a given pressure, the isosteric heats and hydrogen uptakes of CSCNTs with a fixed apex angle both increase with the etching degree. Under a given etching degree, the isosteric heats and hydrogen uptakes of CSCNTs both increase with the decrease of apex angle. Among five possible apex angles, CSCNTs with the apex angle of 19.2° have the best hydrogen storage capacity. Finally, according to the simulated result, an ideal CSCNT structure to obtain the optimal hydrogen storage capacity is proposed.