An X‐ray photoelectron spectroscopy investigation of silver iodide‐coated ion‐selective electrodes

The AgI‐coated ion‐selective electrode surface is more stable than either the AgCl or AgBr surfaces if exposed to solutions containing ions such as Cl−, Br−, I−, Ag+, and NH3 for a week. A mixed AgClsI1− or AgBrsI1−s phase is formed upon a week's treatment of the AgI surface with either Cl− or Br−, with S much smaller than 1. After a week's treatment with high concentrations of the ions, no new surface layer consisting of only AgCl or AgBr is formed, as was observed in the case of AgCl and AgBr electrodes. Although AgI is much less soluble than either AgCl or AgBr, the absorption of chloride and bromide ions into the AgI surface nevertheless increases with time.