Model for Voltammograms of the Under-Potential Deposition of Copper on Solid Gold (111) in the Presence of Bisulfate.

摘要

A model for the underpotential deposition of Cu on Au(lll) in the presence of H2SO4, was recently proposed. In this model we assumed that the HSO4(-) ions formed a square root of 3 x square root of 3 lattice which produced a honeycomb template for the deposition of the copper. This results in the electrodeposition of about 3/3 of the copper of a monolayer, corresponding to the first peak in the voltammogram. The second peak, of about 1/3 of the Cu of the full monolayer, is due to the displacement of the HSO4(-), by copper. In our previous work we assumed that the HSO4(-), template was in place during the whole electrodeposition process. However, from recent experimental evidence we know that this is not so. An improved effective field model in which the electrodeposition potential of the HSO4(-) changes with the amount of adsorbed copper is suggested. This new model reproduces the shape of the first peak of the voltammogram, and explains the transition of a broad peak to a narrow one by a second order phase transition (hard hexagon model) of the adsorbed HSO4(-).