Insights into the H2/CH4 Separation Through Two-Dimensional Graphene Channels: Influence of Edge Functionalization.
Insights into the H2/CH4 Separation Through Two-Dimensional Graphene Channels: Influence of Edge Functionalization.
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通过二维石墨烯通道洞察 H-2/CH4 分离：边缘功能化的影响
DOI：
10.1186/s11671-015-1199-2
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发表时间：
2015-12
影响因子：
--
通讯作者：
Yan Z
中科院分区：
文献类型：
--
作者：
Xu J;Sang P;Xing W;Shi Z;Zhao L;Guo W;Yan Z
采用分子模拟技术研究了H2/CH 4混合气体在相邻石墨烯层间二维通道中的输运.发现具有0.515~0.6 nm孔径的原始石墨烯膜（GM）仅允许H2分子而不是CH 4分子进入，形成分子筛。在孔径为0.64~1.366 nm时，H2和CH 4分子均能进入GM孔道，其中甲烷的渗透性优于氢气，在0.728 nm处CH 4/H2选择性最大（1.89）。通过-H、-F、-OH、-NH 2和-COOH基团的边缘官能化可以通过改变孔的活性表面积和调节与通道入口处的分子的吸引和/或排斥相互作用来显著改变气体渗透性。在孔径为0.6nm时，-H、-F和-OH基团对分子筛的透氢性能有促进作用，而-NH 2、尤其是-COOH对分子筛的透氢性能有抑制作用，透氢率为零。在孔宽为0.64和0.728 nm时，-H和-F边缘官能化的GM均表现出甲烷相对于氢气的优先选择性，而GM-OH的有利传输从0.64 nm处的H2分子变为0.728 nm处的CH 4分子。对于GM-NH 2，在0.64 nm处表现出优异的氢分子筛，然后在0.728 nm处转变为显著的H2/CH 4选择性。同时，小的H2分子开始进入GM-COOH的通道，在孔宽度达到0.728 nm。对于1.336 nm的最大孔宽度，边缘官能化的影响变得很小，并且对于所有考虑的膜观察到可比较的CH 4/H2选择性。本文的在线版本（doi：10.1186/s11671-015-1199-2）包含补充材料，可供授权用户使用。
A molecular simulation technique is employed to investigate the transport of H2/CH4 mixture through the two-dimensional (2D) channel between adjacent graphene layers. Pristine graphene membrane (GM) with pore width of 0.515~0.6 nm is found to only allow H2 molecules to enter rather than CH4, forming a molecular sieve. At pore widths of 0.64~1.366 nm, both H2 and CH4 molecules could fill into the GM channel, where the permeability of methane is more preferential than that of hydrogen with the largest CH4/H2 selectivity (1.89) at 0.728 nm. The edge functionalization by –H, –F, –OH, –NH2, and –COOH groups could significantly alter gas permeability by modifying the active surface area of the pore and tuning attractive and/or repulsive interaction with molecules at the entrance of channel. At the pore width of 0.6 nm, the H2 permeability of molecular sieve is enhanced by –H, –F, and –OH groups but restrained by –NH2, especially –COOH with a passing rate of zero. At pore widths of 0.64 and 0.728 nm, both –H and –F edge-functionalized GMs show a preferential selectivity of methane over hydrogen, while the favorable transport for GM–OH is changed from H2 molecules at 0.64 nm to CH4 molecules at 0.728 nm. For GM–NH2, it exhibits an excellent hydrogen molecular sieve at 0.64 nm and then turns into a significant H2/CH4 selectivity at 0.728 nm. Meanwhile, small H2 molecules start to enter the channel of GM–COOH at the pore width up to 0.728 nm. For the largest pore width of 1.336 nm, the influence of edge functionalization becomes small, and a comparable CH4/H2 selectivity is observed for all the considered membranes. The online version of this article (doi:10.1186/s11671-015-1199-2) contains supplementary material, which is available to authorized users.