Structural properties of silver halide surfaces contacting water

Abstract

The role of the solid-state surface properties of AgCl and AgBr contacting a 1:1 electrolyte with various silver ion concentrations is described. In these cases, the separation of charge carriers in the solid or space charge is shown to coexist with a charge separation in the electrolyte. From alternating-current conductance and capacitance measurements, the dielectric loss can be calculated as a function of frequency. Comparing the data with theory indicates that the space charge potential of the solid varies with not only the concentration of divalent cation impurities in the solid and the temperature, but also with the silver ion concentration of the solution. The potential with respect to bulk solid at zero is found to-be negative, indicating a positive space-charge region. For impure silver halides, the results show that a maximum space charge potential exists near the equivalence point of the silver halide. This maximum shifts to a lower pAg of the solution at higher temperatures. The results further show, however, a small change in the space charge potential as the pAg is varied in the solution. An increase in divalent-cation impurity concentration in silver chloride indicates an increase in the magnitude of the space charge potential.