Theoretical investigation of the effect of graphite interlayer spacing on hydrogen absorption
Theoretical investigation of the effect of graphite interlayer spacing on hydrogen absorption
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DOI：
10.1103/physrevb.76.165404
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发表时间：
2007-10-01
影响因子：
3.7
通讯作者：
Morris, James R.
中科院分区：
文献类型：
--
作者：
Aga, Rachel S.;Fu, C. L.;Morris, James R.
我们用第一性原理计算和经典巨正则蒙特卡罗模拟研究了氢分子在石墨层间的吸收。虽然最近的一项理论研究表明，石墨层在室温下具有很高的存储容量，但以前对氢-石墨系统的模拟结果表明情况并非如此。我们的第一性原理计算表明，如果在能量上不利的初始吸收阶段能够被克服，那么在石墨层之间存储氢分子是可能的。初始吸收的障碍来自于H(2)吸收所需的大晶格应变：少量的初始吸收会导致超过60%的层间膨胀。为了确定在有限的温度(和压力)下是否真的有大量的存储是可能的，我们用可变的石墨层间距进行了宏正则蒙特卡罗H(2)吸收模拟。使用两种不同的H(2)-C相互作用势，我们发现在室温和中等压力下(例如，在298K和5 Mpa下接近2wt%)，H(2)-质量吸收很低。我们的结果表明，在石墨层中，孔宽或层间距在6A左右时具有最佳的吸收能力。
We investigate the absorption of hydrogen molecules between graphite layers using both first-principles calculations and classical grand-canonical Monte Carlo simulations. While a recent theoretical study showed that graphite layers have high storage capacity at room temperature, previous simulation results on hydrogen-graphite systems showed otherwise. Our first-principles calculations suggest that it is possible to store hydrogen molecules between the graphite layers if the energetically unfavorable initial absorption stage could be overcome. The barrier to the initial absorption originates from the large lattice strain required for H(2) absorption: small amounts of initial absorption cause an interlayer expansion of more than 60%. To determine if significant storage is indeed possible at finite temperature (and pressure), we performed grand-canonical Monte Carlo H(2)-absorption simulations with variable graphite interlayer spacing. Using two different potentials for the H(2)-C interaction, we found low-H(2)-mass uptake at room temperature and moderate pressures (e.g., close to 2 wt % at 298 K and 5 MPa). Our results suggest that a pore width or interlayer spacing around 6 A in the graphite layers has the optimum absorption capacity.