Abstract
With the purpose of understanding nature of abnormal electrodeposition during industrial silver electrolysis, relationship between electrolysis conditions and morphology of the deposits was investigated. SEM observation of the deposit on a silver working electrode with 4 mm2 initial surface area was carried out under various silver nitrate concentrations, nitric acid concentrations and applied overpotentials. Crystallographic morphology of the deposit after passing 10 C of electric charge was acicular form when the applied overpotential was low. As the overpotential increased, dendritic deposit tended to grow. Under high overpotential condition, which caused lack of silver ion supply to the electrode, deposit with spongy form was obtained. Change of the morphology was shown to depend on silver ion concentration in the vicinity of the electrode, and fine crystals were obtained when silver nitrate concentration was decreased. Increment in nitric acid also caused fine deposition. Contribution of nitrite ion, which is thermodynamically expected to be generated during electrolysis, was not observed under the conditions employed in this study.
