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

Abstract

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 impurity. In the case of iodine, the mechanism depends in part on the relative strength 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 sulfur, 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 intergranular stress corrosion cracking and semiconductor device processing are discussed.

Nickel Electrodeposition on a Gold Polycrystalline Foil: A Combined Voltammetric and Photoelectron Spectroscopy Study

“…The rinsing procedure is expected to remove the salts of the electrolyte solution so that they will not remain on the electrode surface after water evaporation. In this respect, only the double layer and chemisorbed species will remain on the surface. , To ensure that no nickel adsorbs on the electrode at open-circuit potential, a clean Au foil was transferred to the electrochemical cell and immersed in the solution (at open-circuit potential) for 10 min. XPS examination of the sample after rinsing with Millipore water and transfer back to the UHV chamber showed slight contamination by oxygen and carbon, but no other detectable species.…”

Cu electrodeposition on Ru(0001): Perchlorate dissociation and its effects on Cu deposition

“…Each chamber was pumped by a turbomolecular pump to permit high gas loadings. A detailed description of this system and methodology has been published previously [15]. The surface was characterized by XPS under UHV condition after cleaning it in the main chamber by repeated cycles of Ar ion sputtering followed by annealing.…”

Stability and activity of titanium oxynitride thin films for the electrocatalytic reduction of nitrogen to ammonia at different pH values

“…This system has been previously described. 32,33 Briefly, it consists of a UHV analytical system with XPS and an ion-sputtering gun (the same as used for ex situ film characterization described above), an antechamber with the electrochemical cell, and a smaller sample introduction chamber. Sample emersion from the electrolyte occurs under controlled potential, followed by rinsing in DI water to remove dried electrolyte layers, followed by transfer under vacuum to the UHV analysis chamber.…”