The Frequency Response of Limiting Currents to Sinusoidal Speed Modulation at a Rotating Disk Electrode

When a sinusoidal modulation is superimposed on the rotation speed of a rotating disk electrode, the corresponding modulated current follows the Levich equation closely for sufficiently low ratios of the modulation frequency to the constant center rotational frequency. In this work, the frequency response of the modulated current (amplitude and phase) is derived for the general case and the results experimentally confirmed over a wide range of Schmidt numbers (230-2100 Sc) and modulation to rotational frequency ratios for the reduction of Fe+3 to Fe+2 in 1.0M H2SO4 over the temperature range 25°-85°C. Tables are given of the phase and amplitude factors which would be encountered for the normal range of both modulation and solution parameters.