Enthalpy and entropy effects in hydrogen adsorption on carbon nanotubes.
Enthalpy and entropy effects in hydrogen adsorption on carbon nanotubes.
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DOI：
10.1021/la046757b
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发表时间：
2005-06
期刊：
影响因子：
--
通讯作者：
I. Efremenko;M. Sheintuch
中科院分区：
文献类型：
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作者：
I. Efremenko;M. Sheintuch
利用分子力学、密度泛函理论和从头计算的方法，分析了不同直径的锯齿形单壁碳纳米管（SWCNT）内外表面与氢吸附相关的相互作用能和熵。对于单个分子来说，最强的相互作用是在 (8,0) 纳米管内部发现的，比平面石墨片的相互作用强 3.5。外表面的吸附比石墨弱。由于空间考虑，这两个过程都伴随着极其强烈的熵下降。碳纳米管内缺乏特定的吸附位点和氢分子之间的弱吸引力相互作用导致它们在低温下紧密堆积。利用朗缪尔等温线中计算的几何和热力学参数，我们预测即使在 100 bar 的压力下，SWCNT 在室温下的吸附容量也小于 1 wt%。
Interaction energies and entropies associated with hydrogen adsorption on the inner and outer surfaces of zigzag single-wall carbon nanotubes (SWCNT) of various diameters are analyzed by means of molecular mechanics, density functional theory, and ab initio calculations. For a single molecule the strongest interaction, which is 3.5 greater than that with the planar graphite sheet, is found inside a (8,0) nanotube. Adsorption on the outer surfaces is weaker than that on graphite. Due to the steric considerations, both processes are accompanied by an extremely strong decline in entropy. Absence of specific adsorption sites and weak attractive interaction between hydrogen molecules within carbon nanotubes results in their close packing at low temperatures. Using the calculated geometric and thermodynamic parameters in Langmuir isotherms we predict the adsorption capacity of SWCNTs at room temperature to be smaller than 1 wt % even at 100 bar.