Center for Electrochemistry, Department of Chemistry and Biochemistry, University of Texas at Austin , Austin, Texas 78712, United States.
J Am Chem Soc. 2013 Oct 23;135(42):15890-6. doi: 10.1021/ja407395m. Epub 2013 Oct 11.
We report a new method of scanning electrochemical microscopy (SECM) that can be used to separate multireactional electrochemical interfaces, i.e., electrodes at which two or more reactions occur (and hence two partial currents flow) at the same time. This was done with a modified tip generation/substrate collection mode where the two reactions occur on the tip electrode, and the substrate electrode is held at a potential to collect only one of the products, allowing the determination of the individual partial currents. Thus, by using the substrate electrode current and the difference between the tip and substrate electrode currents, the two reactions occurring on the tip electrode can be separated. As a test case for this new method, we investigated proton reduction on Mn, a reaction that, because of the highly corrosive nature of Mn, to our knowledge has never before been directly measured. This test was carried out using a Mn tip electrode and a Pt substrate electrode. Using a three-dimensional COMSOL Multiphysics simulation, we were able to accurately determine the tip/substrate distance with this electrode, and by fitting simulations to experimental data, we were able to determine an exchange current density, log(j(0)) = -4.7 ± 0.7 A cm(-2), for proton reduction on Mn in strong acid. This result corrects a literature value and was used in a pattern recognition algorithm reported in a companion manuscript.
我们报告了一种新的扫描电化学显微镜（SECM）方法，可用于分离多反应电化学界面，即在同一时间发生两个或多个反应（因此有两个部分电流流动）的电极。这是通过改进的尖端生成/基底收集模式来实现的，其中两个反应发生在尖端电极上，而基底电极保持在收集仅一个产物的电位，从而可以确定各个部分电流。因此，通过使用基底电极电流和尖端与基底电极电流之间的差值，可以分离尖端电极上发生的两个反应。作为这种新方法的测试案例，我们研究了质子在 Mn 上的还原，由于 Mn 的腐蚀性很强，据我们所知，该反应以前从未被直接测量过。该测试使用 Mn 尖端电极和 Pt 基底电极进行。通过使用三维 COMSOL Multiphysics 模拟，我们能够准确地确定该电极的尖端/基底距离，并且通过将模拟拟合到实验数据，我们能够确定 Mn 上质子还原在强酸中的交换电流密度，log(j(0))=-4.7±0.7 A cm(-2)。该结果纠正了文献值，并在一篇同行评审的论文中报告的模式识别算法中使用。
