AC impedance measurements at ultramicroelectrodes

Ultramicroelectrodes the dimensions of which are typically a few microns, have properties which are useful for a wide range of electrochemical studies. As a result of their small size, the rate of mass transport to and from the electrode is increased due to the spherical nature of the diffusion compared with semi-infinite linear diffusion to electrodes of normal dimensions. Also IR drop and double-layer charging currents are reduced. By combining AC impedance spectroscopy with ultramicroelectrodes, a powerful tool is created for characterising an electrochemical system since both Faradaic and non-Faradaic processes may be readily characterised. This powerful technique has applications in the study of batteries, sensors, corrosion, and where impedance measurements must be made on highly resistive media e.g. it is possible to measure the impedance of the solvent in the absence of added electrolyte