Electrochemical Structure of the Plasma–Liquid Interface
Electrochemical Structure of the Plasma–Liquid Interface
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DOI：
10.1021/acs.jpcc.1c09650
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发表时间：
2022-01
期刊：
影响因子：
--
通讯作者：
Trey Oldham;E. Thimsen
中科院分区：
文献类型：
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作者：
Trey Oldham;E. Thimsen
非热大气压等离子体与液体接触产生各种高能光子、离子和电子，它们可以被传输到等离子体-液体界面（PLI）。与常规电化学系统中固体电极和电解质之间形成的电化学界面类似，PLI上的电荷转移过程能够促进还原-氧化（氧化还原）反应。然而，在与液体接触的自由等离子体射流的情况下，固体电极的缺乏模糊了电化学半反应的空间位置。在这里，我们提出了一种空间电化学测量技术，用于表征与大气压等离子体射流接触的水溶液。该技术基于测量位于溶液内不同位置的两个相同的Ag/AgCl电化学电极之间的电势差。更具体地，通过测量本体溶液中位于PLI附近的不同位置处的一个电化学电极相对于位于远离PLI的另一个电化学电极的电势来制作电化学图。图中具有这些电化学电极之间的负电位差和正电位差的区域分别用于识别无电极阴极和阳极。通过多光谱成像的分子比色氧化还原指示剂的空间分布的可视化显示，还原发生在等离子体射流中心线附近，而氧化发生在更远的溶液中，这构成了电化学图的独立确认。
Nonthermal atmospheric pressure plasma in contact with a liquid yields a variety of energetic photons, ions, and electrons, which can be transported into the plasma–liquid interface (PLI). Similar to the electrochemical interface formed between a solid electrode and electrolyte in conventional electrochemical systems, the charge-transfer process across the PLI is able to promote reduction–oxidation (redox) reactions. However, in the case of free plasma jets in contact with liquids, the absence of solid electrodes obscures the spatial locations of the electrochemical half-reactions. Herein, we present a spatial electrochemical measurement technique used to characterize an aqueous solution in contact with an atmospheric pressure plasma jet. The technique is based on measuring the potential difference between two identical Ag/AgCl electrochemical electrodes positioned at different locations within the solution. More specifically, electrochemical maps were made by measuring the potential of one electrochemical electrode positioned at different locations near the PLI with respect to the other electrochemical electrode positioned far away from the PLI in the bulk solution. Regions in the map with negative and positive potential differences between these electrochemical electrodes were used to identify the electrodeless cathode and anode, respectively. Visualization of the spatial distribution of molecular colorimetric redox indicators by multispectral imaging revealed that reduction was occurring near the plasma jet centerline while oxidation was occurring further away in solution, which constitutes an independent confirmation of the electrochemical maps.