Abstract
Chronoamperograms for gold in solutions containing 0.1 M thiourea, 0.5 M H2SO4, and catalytically active sulfide ions at the concentration c 1 from 1 × 10−5 to 4 × 10−5 M are obtained at different potentials with the aid of an automated setup intended for renewing the electrode surface directly in the solution by cutting off a thin surface layer of the metal. It is shown that the results of measurements of the current practically coincide at a constant value of the product c 1 t, where t is the time period elapsed after the renewal of the electrode surface. Such a coincidence testifies to a diffusion nature of processes that hamper accumulation of sulfide ions at the gold surface. This fact permitted the use of a procedure developed previously for the calculation of polarization curves at constant values of surface coverage θ by catalytically active ions. At θ = const, the voltammetric curves for gold in sulfide-containing thiourea solutions are shown to correspond to the Tafel equation. With the surface coverage increasing, the effective values of the exchange current i 0, transfer coefficient α, and anodic reaction order with respect to thiourea P a increase from the values i }~ 10−5 A cm−2, α }~ 0.12, and P a = 0.2, which are characteristic of pure solutions, to 2 × 10−4 A cm−2, α }~ 0.5, and P a = 1.1 (at θ }~ 0.5). An interpretation to the established regularities is given.
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Original Russian Text © R.Yu. Bek, L.I. Shuraeva, 2006, published in Elektrokhimiya, 2006, Vol. 42, No. 4, pp. 340–346.
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Bek, R.Y., Shuraeva, L.I. Kinetics and mechanism of gold dissolution in thiourea solutions: Effect of sulfide ions. Russ J Electrochem 42, 293–298 (2006). https://doi.org/10.1134/S1023193506040021
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DOI: https://doi.org/10.1134/S1023193506040021