This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueous solutions of alkali metal cations (Na⁺, K⁺ and Rb⁺) and iodide anions, monitored by an electrochemical quartz crystal microbalance (EQCM). Different electrode material compositions as well as various electrolyte concentrations have also been considered. By tracking the ions during electrochemical polarization, we aimed to identify the reasons for the fading capacitor performance that occurs during long-term operation. The mass change profile suggests that hydroxide anions are responsible for counterbalancing the charge stored on the negative electrode. Furthermore, we found that iodide-based species are physically adsorbed on the carbon surface immediately after the electrodes come into contact with the electrolyte, regardless of the textural properties of the activated carbon used or electrode composition. Apart from the qualitative description, the mass change profiles allow the sequence of pore occupation to be determined. Additionally, the solvation numbers for alkali metals (Na⁺, K⁺ and Rb⁺) and hydroxide-based species have been determined. It is claimed that the solvation number is strongly affected by the electrolyte composition. Apparently, the concentration of water molecules available in the electrolyte cannot be neglected. The outcome of this research has fundamental and application context.

中文翻译：

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通过EQCM技术监测电化学电容器中特定的碳/碘相互作用

本文报道了各种多孔碳电极/碱金属阳离子水溶液（Na ⁺，K ⁺和Rb ⁺离子和碘化物阴离子，由电化学石英晶体微量天平（EQCM）监控。还已经考虑了不同的电极材料组成以及各种电解质浓度。通过跟踪电化学极化过程中的离子，我们旨在确定长期运行期间电容器性能下降的原因。质量变化曲线表明，氢氧根阴离子负责平衡存储在负极上的电荷。此外，我们发现，无论使用的活性炭或电极组成的质地如何，在电极与电解质接触后，碘化物基物质就会立即物理吸附在碳表面上。除了定性的描述，质量变化曲线可以确定孔的占据顺序。此外，碱金属（Na⁺，K ⁺和Rb ⁺）和基于氢氧化物的物质已经确定。要求溶剂化数受电解质组合物的强烈影响。显然，不能忽视电解质中可用的水分子的浓度。这项研究的结果具有基础和应用背景。