Anodic Silver Oxide (AgO) Layers by XPS

Abstract

XPS data have been obtained from silver oxide (AgO) thin films which were prepared by the anodic oxidation of high purity silver metal in alkaline solution (1M NaOH). The sample preparation included a pre-oxidation at lower potentials to form an Ag2O film on top of the metallic silver electrode, and a second oxidation step to give an AgO film finally. All the electrochemical oxidation was performed under a protecting noble gas atmosphere in a separate chamber flanged to the UHV spectrometer, so that any contact with laboratory air or moisture was avoided. The following spectra will be presented in the present contribution, revealing the high phase purity and quality of the electrochemically grown oxide layers: survey spectrum, spectra of major elements silver and oxygen (Ag 3d and O 1s), spectra of minor element carbon (C 1s). Traces of other elements such as sodium from the electrolyte cannot be detected. In contrast to previously published data of ex-situ prepared powder samples which revealed a huge amount of contaminations, the detailed XPS data evaluation shows that only minor contaminations are present on the electrochemically grown oxides. Therefore, these spectra are extremely useful in XPS-studies of Ag/O-systems such as silver epoxidation catalysts.