Ring-disk electrode study of the anodic behavior of gold in 0.2m Sulfuric acid

The dissolution of gold from a rotating disk electrode was studied in 0.2M H₂SO₄. Gold dissolution was observed at potentials greater than +1.13 V vs. SCE. The rate of dissolution was determined as a function of potential by collecting the gold on a platinum ring electrode. Gold dissolution was also observed during the reduction of gold oxide films. The quantity of this cathodically dissolved gold was found to be a function of the electrode rotation speed, and the amount of gold oxide reduced. The increase in cathodically produced soluble gold with increasing rotation speed was shown to obey first order heterogeneous kinetics. The oxidation state of the cathodically produced gold was found to depend on the potential at which the gold oxide was formed. If the disk electrode was oxidized at E_D< +1.45 V, Au (III) was the predominant species collected at the ring electrode. However, if the oxidizing potential was greater than + 1.45 V, a significant quantity of Au (1) was also collected at the ring electrode.