Oldham Trey, Yatom Shurik, Thimsen Elijah
Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA.
Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ, USA.
Phys Chem Chem Phys. 2022 Jun 15;24(23):14257-14268. doi: 10.1039/d2cp00203e.
Nonthermal plasmas in contact with liquids have been shown to generate a variety of reactive species capable of initiating reduction-oxidation (redox) reactions at the electrochemically active plasma-liquid interface. In conventional electrochemical cells, selective redox chemistry is achieved by controlling the reduction potential at the solid electrode-electrolyte interface by applying a bias an external circuit. In the case of plasma-liquid systems, an analogous means of tuning the reduction potential near the interface has not clearly been identified. When treated as a floating surface, the liquid is expected to adopt a net negative charge to balance the flux of hot electrons and relatively cold positive ions. The reduction potential near the plasma-liquid interface is hypothesized to be proportional to the floating potential, which can be approximated using an analytical model provided the plasma parameters are known. Herein, we present a framework for correlating the electron density and electron temperature of a noble gas plasma jet to the reduction potential near the plasma-liquid interface. The plasma parameters were acquired for an argon atmospheric plasma jet in contact with an aqueous solution by means of laser Thomson scattering. The reduction potential was determined using identical reference electrodes to measure the potential difference between the plasma-liquid interface and bulk solution. Interestingly, the measured reduction potentials near the plasma-liquid interface were found to be in good agreement with the model-predicted values determined using the plasma parameters obtained from the Thomson scattering experiments.
已证明与液体接触的非热等离子体能够产生多种活性物质，这些活性物质能够在具有电化学活性的等离子体 - 液体界面引发氧化还原反应。在传统的电化学电池中，通过在外部电路中施加偏压来控制固体电极 - 电解质界面处的还原电位，从而实现选择性氧化还原化学。在等离子体 - 液体系统中，尚未明确确定一种类似的调节界面附近还原电位的方法。当将液体视为浮动表面时，预计液体会带有净负电荷以平衡热电子和相对较冷的正离子的通量。假设等离子体 - 液体界面附近的还原电位与浮动电位成正比，只要已知等离子体参数，就可以使用分析模型对其进行近似。在此，我们提出了一个框架，用于将惰性气体等离子体射流的电子密度和电子温度与等离子体 - 液体界面附近的还原电位相关联。通过激光汤姆逊散射获取了与水溶液接触的氩气大气等离子体射流的等离子体参数。使用相同的参比电极测量等离子体 - 液体界面与本体溶液之间的电位差，从而确定还原电位。有趣的是，发现等离子体 - 液体界面附近测得的还原电位与使用从汤姆逊散射实验获得的等离子体参数确定的模型预测值非常吻合。
