Abstract
The impact of potential applied to the conductive surface of nanoporous membrane on the membrane potential at zero current is investigated theoretically on the basis of two–dimensional Space–charge model. The membrane separates two reservoirs with different salt concentrations. It is shown that the variation of applied potential from negative to positive values results in the continuous change of membrane selectivity from cation to anion. For equal ion diffusion coefficients, the dependence of membrane potential on the applied potential is an odd function, while for different ion diffusion coefficients it is shifted along the applied potential axis due to contribution of diffusion potential enhanced by the induced charge effect. The decrease of pore radius results in the increase of ionic selectivity and steep transition between cation– selective and anion–selective states when the applied potential is changing
Highlights
Over the last two decades, the development of nanopores and nanochannels with controlled ion transport has attracted a lot of research attention
We theoretically investigate the case when the membrane ionic selectivity is switched by the external potential applied to the conductive nanopore surface
The dependence of membrane potential on the logarithm of concentrations ratio for different surface charge densities is shown in Fig. 2 (a) for an aqueous electrolyte with equal ion diffusion coefficients
Summary
Over the last two decades, the development of nanopores and nanochannels with controlled ion transport has attracted a lot of research attention. The theory of ion transport in electrochemically switchable conductive membranes based on a number of restrictive assumptions showed only satisfactory agreement with the experimental data [22] It was shown in [23] that a qualitative similarity between predicted and measured membrane potential can be obtained with one–dimensional transport model by assuming that the applied voltage gives rise to a fixed charge proportional to it. The two–dimensional Space– Charge model for cylindrical nanopores with constant surface charge density [30, 31] was first extended to the case of constant surface potential in [17] and further applied to description of conductive nanopores in [18, 19] The latter studies were focused on the situation when the nanopore charge is induced only by the electric field resulting from different mobilities of ions diffusing through membrane. The dependence of membrane potential at zero current on the applied voltage, electrolyte type, and pore size is discussed and analyzed
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