Mechanism and Stability Study of Gold Electrodeposition from Thiosulfate-Sulfite Solution

• Published in: Journal of the Electrochemical Society 2014-01, Vol.161 (12), p.D687-D696
• Main Authors: Estrine, E. C., Riemer, S., Venkatasamy, V., Stadler, B. J. H., Tabakovic, I.
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/2.0411412jes

Electrodeposition of gold from a basic "fresh" and "used" thiosulfate-sulfite solution containing 0.02 M Na3Au(S2O3)2 has been investigated on Au and Pt electrodes using various electroanalytical techniques (CV, LSV, RDE), controlled potential electrodeposition, as well as constant current and pulse current deposition. It was proposed that irreversible one electron reduction to gold- run in "fresh" solution-at the Pt electrode starts from Au(S2O3)(SO3)25−, a mixed gold thiosulfate -sulfite complex with a high stability constant (log β = 30.8). A diffusion coefficient of 1.77 × 10−6 cm2/s for Au (S2O3) (SO3)25− was calculated from the slope of the linear plot ip- ν1/2 obtained with a Pt electrode, which is lower than the value of diffusion coefficient (D = 4.6 × 10−6 cm2/s) obtained for the Au (S2O3)23− complex (log β = 26.0) present in the "used" solution. The voltammograms for gold deposition on the Au electrode were significantly different from those on Pt indicating that the electron transfer was influenced by the coupled chemical reaction. The natures of possible chemical reactions are discussed.