HIGH-FREQUENCY IMPEDANCE MEASUREMENTS AT ULTRAMICROELECTRODES

Problems associated with electrochemical ac impedance measurements at frequencies up to 50 MHz are discussed in detail. Limitations in the i mpedance measurements arise from inductance and stray capacitance of l eads connecting electrochemical cell to a measuring circuit. Theoretic al considerations indicate that the best accuracy of measurements can be achieved when working with ultramicroelectrodes 2.5 x 10(-7) to 8 x 10(-6) cm(2). Construction of ultramicroelectrodes suitable for such measurements and a diagram of the electronic circuit is described. Pre liminary results showing frequency dispersion of the double layer capa citance and solution resistance and the kinetics of adsorption of n-bu tanol are presented.