Asymmetric rectified electric and concentration fields in multicomponent electrolytes with surface reactions
Asymmetric rectified electric and concentration fields in multicomponent electrolytes with surface reactions
复制标题
具有表面反应的多组分电解质中的不对称整流电场和浓度场
DOI：
10.1039/d3sm00823a
复制
发表时间：
2023
期刊：
影响因子：
3.4
通讯作者：
Gupta, Ankur
中科院分区：
文献类型：
--
作者：
Jarvey, Nathan;Henrique, Filipe;Gupta, Ankur
最近的实验研究利用多组分电解质溶液中的交流电场和电化学反应来控制胶体组装。然而，迄今为止的理论研究仅限于二元电解质，并且忽略了电化学反应的影响。在本研究中，我们通过分析具有多组分电解质的系统来解决这些限制，同时还放宽了理想阻挡电极以捕获表面电化学反应的影响的假设。通过低外加电势区域的常规扰动分析，我们求解了泊松-能斯特-普朗克方程，并获得了电势和离子浓度的有效方程。通过结合数值和分析计算，我们的分析揭示了一个重要发现：即使离子种类的扩散率相等，电化学反应本身也可以产生不对称整流电场（AREF），即时间平均的长程电场。这一发现扩展了我们的理解，超越了 AREF 仅由扩散性对比产生的传统观念。此外，我们证明电化学反应引起的 AREF 比不对称扩散引起的 AREF 更强。此外，我们报告了不对称整流浓度场（ARCF）的出现，即时间平均的长范围浓度场，这支持了实验中观察到的胶体组装的电扩散电泳机制。我们还推导了 AREF 和 ARCF 的解析表达式，分别强调了离子强度和电荷密度不平衡作为其形成背后的驱动力的作用。本文提出的结果推动了胶体组装领域的发展，并且对于提高对电化学装置中电解质传输的理解也具有重要意义。
Recent experimental studies have utilized AC electric fields and electrochemical reactions in multicomponent electrolyte solutions to control colloidal assembly. However, theoretical investigations have thus far been limited to binary electrolytes and have overlooked the impact of electrochemical reactions. In this study, we address these limitations by analyzing a system with multicomponent electrolytes, while also relaxing the assumption of ideally blocking electrodes to capture the effect of surface electrochemical reactions. Through a regular perturbation analysis in the low-applied-potential regime, we solve the Poisson–Nernst–Planck equations and obtain effective equations for electrical potential and ion concentrations. By employing a combination of numerical and analytical calculations, our analysis reveals a significant finding: electrochemical reactions alone can generate asymmetric rectified electric fields (AREFs), i.e., time-averaged, long-range electric fields, even when the diffusivities of the ionic species are equal. This finding expands our understanding beyond the conventional notion that AREFs arise solely from diffusivity contrast. Furthermore, we demonstrate that AREFs induced by electrochemical reactions can be stronger than those resulting from asymmetric diffusivities. Additionally, we report the emergence of asymmetric rectified concentration fields (ARCFs), i.e., time-averaged, long-range concentration fields, which supports the electrodiffusiophoresis mechanism of colloidal assembly observed in experiments. We also derive analytical expressions for AREFs and ARCFs, emphasizing the role of imbalances in ionic strength and charge density, respectively, as the driving forces behind their formation. The results presented in this article advance the field of colloidal assembly and also have implications for improved understanding of electrolyte transport in electrochemical devices.