Electrochemical study of interfacial charge transfer kinetics

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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.