Near-wall boundary layers at electrode surfaces studied by attenuated total reflection

Part II. Influence of gas bubbles

Abstract

Near-wall effects in the diffusional layer close to an electrode surface due to gas bubbles trapped in a moving fluid have been investigated by ATR. The changes in the optical response in the presence and absence of an electrochemically generated radical ion can be used to probe the approach of gas bubbles to the surface under study. It is shown that two optical effects are operative, a change in reflectance due to the displacement of the electrode–electrolyte double layer and a change in absorbance due to the decrease of the surface radical ion concentration caused by the gas bubbles. The advantage of ATR is that only solution distances from the electrode of the order of the wavelength of light used are probed, thus allowing the study of near-wall effects.