An XPS investigation of the influence of bromide and iodide solutions on the surface of silver chloride coated ion‐selective electrodes

X‐Ray photoelectron spectroscopic (XPS) data of AgCl‐coated, ion‐selective electrodes exposed to solutions containing high concentrations of bromide and iodide ions revealed that the surface properties of the original electrode changed. The mixed phases, AgBr s Cl 1– s and AgI s Cl 1– s , seem to form initially on the electrode surface, with the existence of the AgICl phase much shorter than that of the AgBrCl phase. This indicates that the formation of the Agl surface layer is kinetically faster than the formation of the AgBr layer. In both cases XPS data showed the ultimate formation of AgBr and AgI layers on top of the original AgCl‐coated, ion‐selective electrode surface after being subjected to solutions containing either bromide or iodide ions. The conversion of the crystalline‐coated, chloride‐selective electrode surfaces to AgBr and AgI layers, however, transformed the chloride‐selective electrodes into bromide‐ or iodide‐selective electrodes with electrode properties different from those of the original electrode.