Characteristics of the electrode-solution interface under faradaic and non-faradaic conditions as observed by internal reflecion spectroscopy

Changes in the optical absorbance in the visible spectral region as observed by internal reflection spectroscopy with transparent electrodes have been studied as a function of potential. For non-faradaic conditions this change is related to the electric charge and can be partially explained, both in wavelength and amplitude-dependence, by the variation of the optical constants as related to the free electron model. The absorbance change as a function of time during potential step has been theoretically and experimentally examined. The effect of a homogeneous chemical reaction involving the optically monitored species formed electochemically on the absorbance versus time curve is discussed quantitatively for the catalytic case.