Underpotential Deposition of Copper at Mercaptoalkane Sulfonate-Coated Polycrystalline Gold

Underpotential deposition (UPD) of copper from aqueous sulfuric acid solution onto polycrystalline gold electrodes coated with 2-mercaptoethane sulfonate (MES) or 3-mercapto-1-propane sulfonate (MPS) films has been studied. On the basis of peak shape, the UPD reduction process was inhibited by the organosulfonate film, with the greater inhibition being observed for the MPS film. The inhibitory affects in the UPD can be overcome by deposition at a constant underpotential (0.00 V vs. SCE) for a set time. After this set time (≥60 s) the charge for stripping of the underpotential deposit was equivalent to the charge recorded for UPD stripping at the bare polycrystalline gold surface.