Specular reflectivity studies of the adsorption of halide anions on gold electrodes in 0.2 M HClO 4

Abstract

The specular reflectivity of gold has been measured in 0.2 M HClO4 with and without halide ions present. The reflectivity potential curves depend on the halide concentration at potentials where halide ions are adsorbed. Increasing halide ion concentration decreases the reflectivity with a limiting value approached at higher halide ion concentrations. The decrease in reflectivity produced by anion adsorption also is potential dependent and approaches a limiting value at more anodic potentials. Hysteresis is evident in the reflectivity-potential curves recorded with cyclic linear potential sweeps when the sweep rates and halide ion concentrations are such that diffusion of halide ions to and from the electrode is expected to be rate controlling. Potential-step techniques and simultaneous reflectivity measurements have been used to demonstrate diffusion control of the adsorption kinetics at low halide concentrations.