Zhang Shengsen, Zhang Zhizhong, Chen Shengjie, Zhu Rong
State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084, China.
Anal Chem. 2021 Apr 13;93(14):5882-5889. doi: 10.1021/acs.analchem.1c00226. Epub 2021 Apr 2.
An electric double layer (EDL) generally exists at the interface between a conductive electrode and its adjacent liquid electrolyte. Accurate measurement of the capacitance of EDL is requisite but a great challenge due to the complexity of its variation mechanism correlated with the magnitude and frequency of applied signals and the difficulty in measuring the inner layer potentials across the EDL. Herein, a novel dielectrophoresis (DEP)-based approach is proposed to measure the capacitance of an EDL at a microelectrode/electrolyte interface. The measurement is achieved by employing DEP manipulation to micro polystyrene (PS) spheres suspended in a liquid electrolyte and determining the capacitance of EDL on the microelectrodes from the moving velocities of spheres. This method allows measurement of the capacitances of EDL under alternating current (AC) signals with different magnitudes and frequencies, so that the capacitance change with the magnitude and frequency of the applied signal can be characterized. The method avoids the impedance interference from the liquid electrolyte, external measuring systems, and other crosstalks, enabling an accurate measurement of double layer capacitance. In addition, the inner layer potentials across EDL under different magnitudes and frequencies of applied signals are comprehensively investigated, which facilitates an understanding of the ion behavior at the interfacial boundary that governs external observations of electrochemical reactions. The accurate measurement of the capacitance of EDL is of significance to explore the mechanism of interfacial functioning of electrochemical and bioelectrical devices and systems.
电双层（EDL）通常存在于导电电极与其相邻的液体电解质之间的界面处。准确测量EDL的电容是必要的，但由于其变化机制与施加信号的幅度和频率相关的复杂性以及测量跨EDL的内层电位的困难，这是一个巨大的挑战。在此，提出了一种基于介电电泳（DEP）的新方法来测量微电极/电解质界面处的EDL电容。该测量通过对悬浮在液体电解质中的微聚苯乙烯（PS）球体进行DEP操纵，并根据球体的移动速度确定微电极上EDL的电容来实现。该方法允许在具有不同幅度和频率的交流（AC）信号下测量EDL的电容，从而可以表征电容随施加信号的幅度和频率的变化。该方法避免了来自液体电解质、外部测量系统和其他串扰的阻抗干扰，能够准确测量双层电容。此外，还全面研究了在不同幅度和频率的施加信号下跨EDL的内层电位，这有助于理解在界面边界处控制电化学反应外部观察的离子行为。准确测量EDL的电容对于探索电化学和生物电气设备及系统的界面功能机制具有重要意义。
