title: Insights into the H2/CH4 Separation Through Two-Dimensional Graphene Channels: Influence of Edge Functionalization.
abstract: 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.
authors.affiliation: College of Science, China University of Petroleum, Qingdao, Shandong, 266580, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.affiliation: College of Science, China University of Petroleum, Qingdao, Shandong, 266580, People's Republic of China.
authors.forename: Pengpeng
authors.initials: P
authors.lastname: Sang
authors.affiliation: College of Science, China University of Petroleum, Qingdao, Shandong, 266580, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xing
authors.affiliation: College of Science, China University of Petroleum, Qingdao, Shandong, 266580, People's Republic of China.
authors.forename: Zemin
authors.initials: Z
authors.lastname: Shi
authors.affiliation: College of Science, China University of Petroleum, Qingdao, Shandong, 266580, People's Republic of China. lmzhao@upc.edu.cn.
authors.forename: Lianming
authors.initials: L
authors.lastname: Zhao
authors.affiliation: College of Science, China University of Petroleum, Qingdao, Shandong, 266580, People's Republic of China.
authors.forename: Wenyue
authors.initials: W
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Heavy Oil Processing, Key Laboratory of Catalysis, China University of Petroleum, Qingdao, 266580, People's Republic of China. zfyancat@upc.edu.cn.
authors.forename: Zifeng
authors.initials: Z
authors.lastname: Yan
keywords: Gas separation; Graphene membrane; Molecular dynamics; Two-dimensional channel