Electrochemical study of interfacial charge transfer kinetics

我们研究的过程发生在微小的电极（直径100纳米至10微米）放置在电解质溶液。我们对施加在这些电极上的交变电位（激励波形）驱动的化学和物理过程特别感兴趣。在许多情况下，即使使用非常高的激励频率（在MHz和GHz范围内），激励波形也会导致电极表面发生还原/氧化过程。由于电化学系统通常是非线性的，因此在此类实验中观察到的平均电流不为零（该电流称为法拉第整流电流）。通过监测法拉第整流电流，我们可以研究极快的电极过程。我们计划使用法拉第整流作为一种工具来探索现有的电子转移过程理论。了解电子传递过程对于开发更好的化学传感器、开发新能源相关技术和生命科学具有重要意义。我们还将使用类似的工具来研究吸附动力学和电解质溶液中的弛豫过程。然而，激励波形不仅可以产生整流电流，还可以产生热量（当振幅足够高且溶液电阻足够低时发生）。加热发生在电极周围很小的区域，但该区域的温度可能超过溶剂的沸点100ºC以上（我们称这种电极为热微电极）。我们计划使用一个热微电极（附在一个电动微定位器上）作为扫描探针。这种仪器将有能力对浸在电解质溶液中的衬底的热导率进行成像。此外，通过改变施加到扫描探针上的交流电压的振幅，它将提供局部加热衬底的可能性。我们认为，这种工具可能有许多用途，特别是在生物和医学研究方面。也许，人们可以使用热微电极杀死恶性细胞。

We study processes occurring on tiny electrodes (100 nm to 10 µm in diameter) placed in solutions of electrolytes. We are especially interested in chemical and physical processes driven by an alternating potential (excitation waveform) applied to these electrodes. In many cases, the excitation waveform causes reduction/oxidation processes to occur at the electrode surface, even if very high excitation frequencies (in a MHz and a GHz range) are used. Since electrochemical systems are, in general, non-linear, the average current observed in such experiments is not zero (that current is called the faradaic rectification current). By monitoring faradaic rectification currents we can investigate extremely fast electrode processes. We are planning to use faradaic rectification as a tool for probing existing theories of electron transfer processes. Understanding of electron transfer processes is important for the development of better chemical sensors, for the development of new energy related technologies and in life science. We will also use a similar tool to investigate the dynamics of adsorption and to study relaxation processes in solutions of electrolytes. Yet, the excitation waveform can generate not only rectification currents but also heat (that happens when the amplitude is sufficiently high and the solution resistance sufficiently low). The heating occurs in a very small zone around the electrode, but the temperature in that zone may exceed the boiling point of solvent by more than 100 ºC (we call such an electrode a hot microelectrode). We are planning to use a hot microelectrode (attached to a motorized micropositioner) as a scanning probe. Such an instrument will have the capability of imaging the thermal conductivity of a substrate immersed in a solution of electrolyte.  In addition, it will offer the possibility of locally heating the substrate by changing the amplitude of the alternating voltage applied to the scanning probe. We believe that such an instrument may have many applications, particularly in biological and medical research. Perhaps, one could use hot microelectrodes to kill malignant cells.