The effects of ion adsorption on the potential of zero charge and the differential capacitance of charged aqueous interfaces
The effects of ion adsorption on the potential of zero charge and the differential capacitance of charged aqueous interfaces
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DOI：
10.1088/1361-648x/aaa4d4
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发表时间：
2018-01
期刊：
影响因子：
--
通讯作者：
Y. Uematsu;R. Netz;D. J. Bonthuis
中科院分区：
文献类型：
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作者：
Y. Uematsu;R. Netz;D. J. Bonthuis
使用箱剖面近似的非静电表面吸附势的阴离子和阳离子，我们计算的微分电容的水电解质界面的泊松-玻尔兹曼方程的数值解，包括离子和不均匀的介电轮廓之间的空间相互作用。正（负）离子的优先吸附使微分电容的最小值向正（负）表面电位值移动。的趋势是类似的零电荷的电位，但是，零电荷的电位不对应于最小的微分电容的情况下的不对称离子吸附，相反的假设通常用于确定零电荷的电位。我们的模型可以用来获得更准确的估计从微分电容或电毛细管测量的离子吸附性能。不对称离子吸附也影响微分电容曲线中作为表面电位的函数的特征最大值的相对高度，但即使对于强吸附电位，该影响也很小，使得难以从峰高可靠地确定吸附性质。
Using a box profile approximation for the non-electrostatic surface adsorption potentials of anions and cations, we calculate the differential capacitance of aqueous electrolyte interfaces from a numerical solution of the Poisson–Boltzmann equation, including steric interactions between the ions and an inhomogeneous dielectric profile. Preferential adsorption of the positive (negative) ion shifts the minimum of the differential capacitance to positive (negative) surface potential values. The trends are similar for the potential of zero charge; however, the potential of zero charge does not correspond to the minimum of the differential capacitance in the case of asymmetric ion adsorption, contrary to the assumption commonly used to determine the potential of zero charge. Our model can be used to obtain more accurate estimates of ion adsorption properties from differential capacitance or electrocapillary measurements. Asymmetric ion adsorption also affects the relative heights of the characteristic maxima in the differential capacitance curves as a function of the surface potential, but even for strong adsorption potentials the effect is small, making it difficult to reliably determine the adsorption properties from the peak heights.