Adsorbate-catalyzed anodic dissolution and oxidation at surfaces in aqueous solutions

Certain adsorbates, particularly sulfur and iodine, present at submonolayer coverages catalyze anodic dissolution or oxidation at selected transition metal surfaces. No change in adsorbate surface coverage or oxidation state is observed during the dissolution process, indicating that the process is truly catalyzed by the adsorbed impurity. This allows enhanced dissolution to take place in environments entirely free of solvated forms of the impuri ty. In the case of iodine, the mechanism depends in part on the relative st rength of iodine-metal vs. metal-metal bond strengths, but also depends on other factors that are as yet poorly understood. In the case of adsorbed su lfur, the effect is related to the ability of adsorbed sulfur to hinder the formation of an oxide layer via the complete dissociation of water at the solid surface. The relevance of these adsorbate-catalyzed processes to inte rgranular stress corrosion cracking and semiconductor device processing are discussed. Copyright (C) 2001 John Wiley & Sons, Ltd.