氢气在单壁碳纳米管束的吸附的密度泛函研究

作者利用密度泛函理论（DFT）计算了氢气在单壁碳纳米管束（SWNTs)中管内 和管间的吸附。考察了温度，孔径以及压力对吸附的分子数密度，重量百分比，单 位体积储存能力以及超额吸附量的影响。DFT计算发现，较大的孔径有利于氢气在 SWNTs中的吸附且氢气在管隙中的吸附不可忽略。计算表明在77 K和6 MPa时，氢气 在2.719 mm的SWNTs的总的吸附的重量百分比分别可达到13.2 wt%，这约是美国能 源部（DOE）目标值的两倍，而单位体积储存能力在DOE目标值附近，而在300 K和 6 MPa时，氢气在2.719 nm的SWNTs的总的吸附的重量百分比仅为1.5 wt%。通过实 验结果与计算结果的比较表明，密度泛函理论的计算结果支持SWNTs有较高的吸附 储氢能力的实验结论。

A Density Functional Study of Hydrogen Adsorption i Single-Walled Carbon Nanotube Arrays

The density functional theory (DFT) is used to estimate hydrogen adsorption in single walled carbon nanotube (SWNT) arrays. Gravimetric storage density, excess gravimetric storage density, and volumetric storage capacity of hydrogen inside the tubes and in the interstices formed by external surfaces of the neighboring carbon tubes in square packed SWNT arrays have been investigated for the tube diameters of 1 225 nm, 2 04 nm and 2 719 nm at 77 K and 300 K. The results of DFT calculations indicate that adsorption in the interstices of large pores is not negligible even when the interstitial spacing is set to 0 334 nm. The calculations indicate that the storage capacity of square arrays of SWNT for a range of configurations exceed 6 5 wt%, the target set by the Department of Energy (DOE) of US, at 77 K. The gravimetric hydrogen storage for 2 719 nm SWNT arrays at 77 K and 6 MPa can reach 13 2 wt%, about two times of the target, while the volumetric capacity is below but near to the equivalent volumetric density of the target. However, the gravimetric hydrogen storage of 1 5 wt% is found at 300 K, far below the DOE standard. Our results suggest that SWNT arrays are promising hydrogen storage material at low temperature, in particular. In addition, the storage capacities from the DFT calculations for SWNT arrays at 77 K and 300 K are in reasonable agreement with experimentally measured capacities.