Segregation Structures and Miscellaneous Diffusions for Ethanol/Water Mixtures in Graphene-Based Nanoscale Pores

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• 作者：Mengyao Zhao ; Xiaoning Yang
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：September 17, 2015
• 年：2015
• 卷：119
• 期：37
• 页码：21664-21673
• 全文大小：840K
• ISSN：1932-7455

文摘

Molecular dynamics simulation was conducted to study ethanol鈥搘ater mixtures and the corresponding pure species, confined within slit-shaped graphene nanopores. Extensive structural and dynamical properties of the confined fluids, including hydrogen-bonding behavior, were investigated. The effects of pore width and mixture composition on the confined behavior were illustrated. It is observed that a layered structure is formed within the confined spaces and the ethanol鈥搘ater mixtures show segregation at larger pores, with ethanol molecules preferentially adsorbing on graphene surfaces. This microphase demixing behavior stems from the competitive effect of the solid鈥揻luid and fluid鈥揻luid interactions. Moreover, miscellaneous diffusion mechanisms have been revealed for the hydrogen-bonding mixtures within the graphene pores. In the mixtures, water and ethanol generally display analogous diffusion mechanism due to ethanol鈥搘ater association, converting from short-time subdiffusion to long-time Fickian diffusion in the larger nanopores. In the smaller pore (7 脜), both ethanol and water show a suppressed single-file diffusion behavior at the initial time and then display subdiffusion or single-file diffusion behavior. The complex diffusion behavior of ethanol鈥搘ater mixtures can be described by the collaborating effects of pore confinement and enhanced interaction in the hydrogen-bonding mixtures.