Interferometric Study of the Concentration Change at High Cathodic Current Densities

The refractive index change, An, i.e., the concentration of the solution at a vertical cathode was studied by a Lloyd mirror laser interferometer during the electrodeposition f copper from CuSO4 solutions with and without ten-fold excess of H2SO4. The initial galvanostatic transients were studied below the limiting current density and above to the start of H ~ bubble formation. It was found that the concentration decreased l inearly with it I/2 for both solu-tions. The effect of an assumed linear refractive index gradient on the mea-sured value of ~n is discussed in addition to the influence of the H2SO4 sup-porting electrolyte. The change of the refractive index, i.e., concentration of the solution in the diffusion layer during electro-chemical processes, has been extensively studied by interferometry, mainly at low current densities (1). At high current densities, the refractive index change o