EQCM study of the dissolution of gold in thiosulfate solutions

The anode behavior of gold in 0.1 M Na2S2O3 at the background of 0.5 M CH3COONa (pH 8.5) was studied on the fresh electrode surface by means of EQCM and voltammetry. The oxidation of thiosulfate causes complete passivation of gold at a potential more positive than 0.8 V. Within the potential range from the open circuit potential (OCP) value to approximately 0.5 V (SHE), no passive layer is formed on the electrode surface and the dissolution of gold anode is observed. The rate of gold dissolution in thiosulfate solution is small on its own (not more than 20 μА cm− 2), but not as a result of electrode passivation by the products of thiosulfate oxidation. Attention is paid to the similarity of the kinetics of gold dissolution in electrolytes for which the formation of a single soluble type of complexes is typical, namely, linear complexes Au(I) with two ligands L-Au-L.