Theory of Faradaic distortion: Equation for the second-harmonic current

Abstract

An equation is derived for the magnitude of the second-harmonic current under ax. polarographic conditions. It is shown that the concentration changes of the depolarizer at the electrode surface do not contain second-harmonic components. The theory permits determination of the rate constant and transfer coefficient, for processes of greater speed than are amenable to elucidation by faradaic-impedance measurements. Furthermore, the major experimental difficulties in faradaic-impedance studies (base current, voltage drop in the series resistances) are virtually absent in second-harmonic work. Second-harmonic studies also promise to be advantageous in the elucidation of adsorption effects in electrochemical reactions.