Surface potentials of conductors in electrolyte solutions

Olga I. Vinogradova, Elena F. Silkina, Evgeny S. Asmolov
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Abstract

When we place conducting bodies in electrolyte solutions, their surface potential $\Phi_s$ appears to be much smaller in magnitude than the intrinsic one $\Phi_0$ and normally does not obey the classical electrostatic boundary condition of a constant surface potential expected for conductors. In this paper, we demonstrate that an explanation of these observations can be obtained by postulating that diffuse ions condense at the "wall" due to a reduced permittivity of a solvent. For small values of $\Phi_0$ the surface potential responds linearly. On increasing $\Phi_0$ further $\Phi_s$ augments nonlinearly and then saturates to a constant value. Analytical approximations for $\Phi_s$ derived for these three distinct modes show that it always adjusts to salt concentration, which is equivalent to a violation of the constant potential condition. The latter would be appropriate for highly dilute solutions, but only if $\Phi_0$ is small. Surprisingly, when the plateau with high $\Phi_s$ is reached, the conductor surface switches to a constant charge density condition normally expected for insulators. Our results are directly relevant for conducting electrodes, mercury drops, colloidal metallic particles and more.
电解质溶液中导体的表面电位
当我们把导电体放置在电解质溶液中时,它们的表面电势 $\Phi_s$ 似乎在量级上远远小于本征离子 $\Phi_0$ ,并且通常不服从导体预期的恒定表面电势的经典静电边界条件。在本文中,我们证明可以通过假设扩散离子在 "壁 "处凝结是由于溶剂的介电常数降低而得到这些观察结果的解释。对于较小的 $\Phi_0$ 值,表面电势呈线性响应。当 $\Phi_0$ 进一步增大时,$\Phi_s$ 非线性地增大,然后饱和到一个恒定值。针对这三种不同模式得出的 $\Phi_s$ 的分析近似值表明,它总是随盐浓度而调整,这相当于违反了恒定电势条件。后者适用于高稀释溶液,但前提是 $\Phi_0$ 较小。令人惊讶的是,当达到高 $\Phi_s$ 的高原时,导体表面会切换到绝缘体通常预期的恒电荷密度条件。我们的结果与导电电极、汞滴、胶体金属颗粒等直接相关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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