Spectroscopic Observation of an Electrochemical Reaction by Means of Internal Reflection

Abstract

In 1962 we performed the following experiments. Silver chloride internal reflection elements were coated with thin palladium films and infra red internal reflection spectra taken with organic liquids contacting the metal films. A metal film 40 A thick gave spectra of the organics similar to attenuated total reflection (ATR) spectra. A thicker film (ca. 175 A thick per chemical analysis) having a resistance of 40 Ω per square also gave spectra of the organics, but with less intensity. These simple experiments showed that spectra of the region close to the electrode could be taken through a thin metal electrode. These results were reported by Hansen and Osteryoung(1) with the suggestion that this type of optical set-up could be used to study electrochemical reactions in situ. It was also suggested that an electrical conductor like germanium could serve as both internal reflection element and electrode. Later in 1962 glass multiple reflection elements were coated with various metals, and spectra of dyes taken in the visible. When the metal film was made an electrode in an electrochemical cell, and a potential applied, large changes in reflectance were observed. These were the beginnings of a fruitful coupling of two fields, internal reflection spectroscopy and electrochemistry.