Interfacial electrodeposition of silver: The role of wetting

Electrodeposits of silver at the water-organic or water-air interfaces are studied for a variety of organic liquids. The morphology of the deposit, its texture, color, and sheen, and the overall rate of its formation are investigated. The organic phase is found to play an important role in determining the character of the deposit, which can range from fast, two-dimensional, highly ramified and lustrous growths to much slower, compact, and black patterns. We show that these are controlled mainly by the contact angle established at the three-phase boundary formed by the two liquids and the emerging deposit, which determines the access of the ions to the growing front. A critical surface tension for the organic solvent is predicted, above which no wetting of the deposit's edge by the water occurs, and compact, black deposits are expected. The measurements verify this prediction and its consequences for the morphology of the deposits.