Potential dependence of anodic current transients on the renewed gold surface in thallium-containing thiosulfate solutions

Abstract

The effect of potential on the anodic current transient times τp, which were measured on the gold electrode surface renewed by cutting off a thin surface metal layer immediately in the thallium-containing thiosulfate solutions of compositions (M): 0.05 Na2S2O3, 10−5 to 10−4 TlNO3, and 0.25 K2SO4, is studied. It is shown that the logarithm of inverse transient times 1/τp linearly depends on the electrode potential. Using the microgravimetrical method, it is found that, in the studied potential range, the amount of chemisorbed thallium ions only slightly depends on the potential, and at E = 0.3 V, it is approximately 0.12 μg/cm2. It is evidenced that the transients reaches a plateau, when an equilibrium surface concentration of catalyst is reached. The value 1/τp reflects the rate of electrochemical oxidation of preliminarily adsorbed thallium(I) ions with the formation of catalytically active thallium(III) ions, and the first electron transfer is the limiting stage of the process.