Department of Chemistry , Kyushu University , Fukuoka 819-0395 , Japan.
Fachbereich Physik , Freie Universität Berlin , 14195 Berlin , Germany.
Langmuir. 2018 Aug 7;34(31):9097-9113. doi: 10.1021/acs.langmuir.7b04171. Epub 2018 Mar 29.
We construct an analytical model to account for the influence of the subnanometer-wide interfacial layer on the differential capacitance and the electro-osmotic mobility of solid-electrolyte interfaces. The interfacial layer is incorporated into the Poisson-Boltzmann and Stokes equations using a box model for the dielectric properties, the viscosity, and the ionic potential of mean force. We calculate the differential capacitance and the electro-osmotic mobility as a function of the surface charge density and the salt concentration, both with and without steric interactions between the ions. We compare the results from our theoretical model with experimental data on a variety of systems (graphite and metallic silver for capacitance and titanium oxide and silver iodide for electro-osmotic data). The differential capacitance of silver as a function of salinity and surface charge density is well reproduced by our theory, using either the width of the interfacial layer or the ionic potential of mean force as the only fitting parameter. The differential capacitance of graphite, however, needs an additional carbon capacitance to explain the experimental data. Our theory yields a power-law dependence of the electro-osmotic mobility on the surface charge density for high surface charges, reproducing the experimental data using both the interfacial parameters extracted from molecular dynamics simulations and fitted interfacial parameters. Finally, we examine different types of hydrodynamic boundary conditions for the power-law behavior of the electro-osmotic mobility, showing that a finite-viscosity layer explains the experimental data better than the usual hydrodynamic slip boundary condition. Our analytical model thus allows us to extract the properties of the subnanometer-wide interfacial layer by fitting to macroscopic experimental data.
我们构建了一个分析模型，以解释亚纳米宽界面层对固-电解质界面微分电容和电动迁移率的影响。该界面层通过介电特性、粘度和平均离子力的离子势的盒子模型被纳入泊松-玻尔兹曼和斯托克斯方程。我们计算了微分电容和电动迁移率作为表面电荷密度和盐浓度的函数，同时考虑了离子之间的空间相互作用。我们将我们的理论模型与各种系统（电容的石墨和金属银，电动数据的氧化钛和碘化银）的实验数据进行了比较。使用界面层的宽度或平均离子力势作为唯一的拟合参数，我们的理论很好地再现了银的微分电容随盐度和表面电荷密度的关系。然而，石墨的微分电容需要额外的碳电容来解释实验数据。我们的理论对于高表面电荷的电动迁移率给出了幂律依赖性，使用从分子动力学模拟中提取的界面参数和拟合的界面参数来再现实验数据。最后，我们检查了电动迁移率的幂律行为的不同类型的流体动力学边界条件，表明有限粘度层比通常的流体动力学滑移边界条件更好地解释了实验数据。因此，我们的分析模型允许我们通过拟合宏观实验数据来提取亚纳米宽界面层的性质。
