A study on hydrogen adsorption behaviors of open-tip carbon nanocones
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Hydrogen adsorption behaviors of single-walled open-tip (tip-truncated) carbon nanocones (CNCs) with apex angles of 19.2° at temperatures of 77 and 300 K were investigated by the molecular dynamics simulations. Four nanomaterials (including three CNCs with different dimensions and a reference CNT) were analyzed to examine the hydrogen adsorption behaviors and influences of cone sharpness on the behaviors of the CNCs. Physisorption of hydrogen molecules could be observed from the distribution pattern of the hydrogen molecules adsorbed on the nanomaterials. Because of the cone geometry effect, the open-tip CNCs could have larger storage weight percentage and less desorption of hydrogen molecules (caused by the temperature growth) on their outer surfaces, as compared with those of the reference CNT. The hydrogen molecules inside the CNCs and the reference CNT, however, were noted to have similar desorption behaviors owing to the confinement effects from the structures of the nanomaterials. In addition, the sharper CNC could have higher storage weight percentage but the cone sharpness does not have evident enhancement in the average adsorption energy of the CNC. Combination of confinement and repulsion effects existing near the tip region of the CNC would be responsible for the non-enhancement feature.
KeywordsPhysisorption Desorption Cone geometry effects Molecular dynamics simulations Modeling and simulation
The author gratefully acknowledges the support provided to this research by the National Science Council of the Republic of China under Project Grant No. NSC 99-2221-E344-003. The assistance by Miss Chen-Yin Tai in data managing during the project period is also acknowledged. The author also thanks the editor and referees for their helpful recommendations to make this paper more readable.
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