THE INFLUENCE OF ORGANIC ADDITIVES ON THE UNDERPOTENTIAL DEPOSITION OF CU ON PT(111)

The influence of hydroquinone, coumarin and crystal violet on the underpotential deposition of Cu on Pt(111) in sulphuric acid solution has been studied over a wide range of concentrations by cyclic voltammetry. All three additives are found to strongly affect the deposition behaviour, while comparatively little influence on the dissolution process is noted. It is therefore concluded that the organic molecules interact strongly with the uncovered Pt(111) surface, blocking sites for Cu deposition, while little interaction apparently exists with the Cu-covered substrate. With hydroquinone present in the solution, two distinctly different Cu deposition potentials are observed, which are assigned to deposition on hydroquinone-covered and -free Pt(111) surface areas. Hence the underpotential deposition of Cu can be used to monitor the adsorption behaviour of the additives.