Structure and Dynamics of Molecular Hydrogen in the Interlayer Pores of a Swelling 2:1 Clay by Neutron Scattering
Structure and Dynamics of Molecular Hydrogen in the Interlayer Pores of a Swelling 2:1 Clay by Neutron Scattering
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DOI：
10.1021/jp5082356
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发表时间：
2014-11-06
影响因子：
3.7
通讯作者：
Youngs, Tristan G. A.
中科院分区：
文献类型：
--
作者：
Edge, Jacqueline S.;Skipper, Neal T.;Youngs, Tristan G. A.
中子散射已被用来揭示的结构和动力学的分子H-2物理吸附到二维孔隙的微水化钙锂皂石粘土。在真空下在415 K下对粘土进行热预处理，得到的夹层组成在1.01.5个水分子/Ca 2+阳离子范围内，并提供了2.82 A的空廊道高度。该值与分子氢的直径非常匹配，并且允许H-2嵌入直至在粘土内形成液体状单层。在0.1 H-2/阳离子的低覆盖度下，等量吸附热为9.2 kJmol（-1）。在40-100 K进行的准弹性中子散射实验揭示了两个人口的H-2的粘土。首先，我们发现分子定位接近部分水合的Ca 2+阳离子。其次，我们确定了一个更移动的液体样人口的运动被捕获的跳跃扩散。在40 K时，H-2扩散系数为2.3 +/- 0.5 x 105 cm（2）s（-1）。这比从大量液体H-2外推的值慢一个数量级。
Neutron scattering has been used to reveal the structure and dynamics of molecular H-2 physisorbed into the two-dimensional pores of sparingly hydrated Ca-laponite clay. Thermal pretreatment of the clay at 415 K under vacuum yielded an interlayer composition in the 1.01.5 water molecules per Ca2+ cation range and provided a vacant gallery height of 2.82 A. This value is very well matched to the diameter of molecular hydrogen and allows intercalation of H-2 up to the point where a liquid-like monolayer is formed within the clay. At a low coverage of 0.1 H-2 per cation the isosteric heat of adsorption is 9.2 kJmol(-1). Quasielastic neutron scattering experiments conducted at 40-100 K reveal two populations of H-2 within the clay. First, we find molecules that are localized close to the partially hydrated Ca2+ cations. Second, we identify a more mobile liquid-like population whose motion is captured by jump diffusion. At 40 K, the H-2 diffusion coefficient is 2.3 +/- 0.5 x 105 cm(2) s(-1). This is an order of magnitude slower than the value extrapolated from bulk liquid H-2.