Concentration Profile of Cu2+ Ion near a Plane Vertical Cathode in Electrolytes Containing CuSO4 and an Excess of H 2 SO 4 as a Supporting Electrolyte

Abstract

The concentration profile of Cu2+ ion was measured near a plane vertical cathode placed in aqueous solution containing CuSO4 and an excess of H2SO4 as a supporting electrolyte. It is known that the absorption bands of cupric ion near the infra-red region and hydrogen ion in the ultraviolet region are widely separated. The distribution of absorbance of electrolyte at a wavelength of about 800 nm was measured near the cathode surface by an image sensor with a resolution power of 4.4 μm. The experimental results coincided well with the theoretical calculation. Under the presumption of an excess of supporting electrolyte and a uniform distribution of current density, a factor was proposed to explain the effect of migration due to the accumulated H+ ion, and the variation of transport properties, on the natural convection along the cathode surface. This factor can be used for the conversion of correlations established in aqueous CuSO4 solution to the correlations in CuSO4-H2SO4 solution, as long as the similarity of velocity and concentration profiles is maintained in these solutions. The usefulness of this factor is demonstrated in the prediction of the interfacial concentration differences of Cu2+ and H+ ions. © 1983, The Electrochemical Society, Inc. All rights reserved.