The size-sieving properties of a mesoporous carbon membrane were studied via molecular permeation and cyclic voltammetry experiments. Two phenomena, simple diffusion and electrochemically aided diffusion, were investigated. Molecular diffusion through the membrane was caused by a concentration gradient across the membrane and was facilitated by electrosorption of ions under an externally applied electric field. The diffusion of molecules transported through the membrane was characterized by the values of permeability and apparent diffusion coefficient in the membrane. Because larger molecules are more restricted in terms of penetrating the pores, the size-based selectivity of the mesoporous carbon membrane could be readily observed. For example, in the two-component permeation experiment, a high selectivity (α = 56.9) of anilinium over Rhodamine B was found. It is inferred that the diffusive transport of the larger Rhodamine B molecules with a more extensive retardation comes from the competitive mechanism between the two kinds of molecules in accessing the pore. A series of voltammetric experiments involving a mesoporous carbon membrane immersed in various electrolytes with ions of different sizes allowed the observation of ion-exclusion phenomena. It was found that the size effect is significant for electrochemically aided diffusion and electrosorption processes. The number of cations inside the pores of the membrane decreases with increasing cation size. This phenomenon is due to the size-exclusion effect, which could be demonstrated by the values of electrical double-layer capacitance for sodium, magnesium, and tetrahexylammonium cations, at potentials ranging from negative values to the point of zero charge, corresponding to 86.7, 73.1, and 50.0 F/g, respectively. The findings of this work manifest that the relationship between the pore size and the dimensions of the molecules determines the transport and sorption behavior of nanoporous carbon materials.
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机译：通过分子渗透和循环伏安法研究了介孔碳膜的筛分特性。研究了两种现象，简单扩散和电化学辅助扩散。通过膜的分子扩散是由整个膜上的浓度梯度引起的，并且通过在外部施加的电场下离子的电吸附得以促进。通过膜的分子渗透性和表观扩散系数的值表征了分子通过膜的扩散。因为较大的分子在穿透孔方面受到更多限制，所以可以容易地观察到介孔碳膜基于尺寸的选择性。例如，在两组分渗透实验中，发现对罗丹明B的苯胺选择性高（α= 56.9）。可以推断，较大的若丹明B分子具有更广泛的阻滞作用的扩散运输是由于两种分子之间进入孔道的竞争机制所致。一系列的伏安实验涉及将中孔碳膜浸在各种电解质中，离子的大小不同，可以观察到离子排斥现象。已经发现，尺寸效应对于电化学辅助的扩散和电吸附过程是显着的。膜孔内的阳离子数量随阳离子尺寸的增加而减少。这种现象是由于尺寸排他效应引起的，这可以通过钠，镁和四己基铵阳离子的双电层电容值来证明，其电势范围为负值到零电荷点，相当于86.7，分别为73.1和50.0 F / g。这项工作的发现表明，孔径与分子尺寸之间的关系决定了纳米多孔碳材料的传输和吸附行为。
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