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

The influence of hydroquinone, coumarin and crystal violet on the unde rpotential 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 beha viour, while comparatively little influence on the dissolution process is noted. It is therefore concluded that the organic molecules intera ct strongly with the uncovered Pt(111) surface, blocking sites for Cu deposition, while little interaction apparently exists with the Cu-cov ered substrate. With hydroquinone present in the solution, two distinc tly different Cu deposition potentials are observed, which are assigne d to deposition on hydroquinone-covered and -free Pt(111) surface area s. Hence the underpotential deposition of Cu can be used to monitor th e adsorption behaviour of the additives.