Chronopotentiometric and voltammetric behaviors of silver ion at carbon paste electrode

Voltammetry at solid electrode. III

Abstract

The deposition of silver on a solid electrode by chronopotentiometry and voltammetry with linearly varing potential was investigated by using carbon paste electrode or platinum disk electrode. Since the usable potential range of the carbon paste electrode in Britton Robinson buffer solution is limited by the decomposition potentials of water, the effect of pH of the buffer solution was studied. It was recognized that the iR drop in the electrode itself affected the shape of the chronopotentiogram and its transition time. The transition time constants were determined within a relative error of ±3%. The plot of log (√τ-√t)/√τ vs. potential (vs. SCE) was linear with the reciprocal slope 79 mV. The ratio of transition time for the cathodi. scan (τ_c) and that for the anodic scan (τ_a) was aboet 1. The transition time constants were almost independent of the current densities.
Silver ion in the range of 0.01 to 0.08 mM is determined sucessfully in 0.1 or 1 M potassium nitrate solution referring to a calibration curve, although the theoretical value of the peak current of silver ion by the Voltammetry with linearly varing potential did not accord with the experimental values, because the aging effect on the activity of the deposited silver was not known.