XPS Studies on Emersed Silver Electrodes: Coverage and Bonding State of Specifically Adsorbed Chloride

The coverage of chloride adsorbed on a silver electrode has been measured as a function of potential using ex situ x-ray photoelectron spectroscopy (XPS). Two types of chlorine have been observed. A specifically adsorbed chlorine species with its Cl 2p3/2 electron binding energy around 198.6 eV represents the major adsorbant. Its coverage depends strongly on the electrode potential and its concentration in the bulk electrolyte. The minor component appears at a lower electron binding energy of 197.3 eV, characteristic of ionicly bonded chlorine. This species increases in coverage relative to the higher energy form after a so-called oxidation-reduction cycle. With this, an independent experimental support is provided for the recent concept of the chemical nature of surface-enhanced Raman-active sites involving low metal oxidation states. © 1990, The Electrochemical Society, Inc. All rights reserved.