Kinetics of the Electrochemical Reduction of Dicyanoaurate

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Abstract
The mechanism of the electrochemical reduction of dicyanoaurate was studied by means of steady‐state and relaxation methods in combination with a rotating disk electrode. The deposition of soft gold, lead‐doped soft gold and cobalt‐hardened gold was found to proceed via one common mechanism that involves adsorption equilibria preceding and following the electron transfer step. Special effects, such as epitaxy and preferred orientation of soft gold, the small‐grained texture of hard gold, and the lead‐induced depolarization of soft gold plating are explained in terms of the energetic states of the adsorbed, oxidized, and reduced gold species. The effect of lead is to lower the activation energy of the electron transfer, which results in the accelerated establishment of a preferred orientation. Cobalt increases the activation energy of the electron transfer and gives rise to a high nucleation rate. The proposed mechanism is shown to explain equally well the anodic behavior of gold in alkaline cyanide electrolyte.

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