PHOTOELECTROCHEMICAL STUDY OF PASSIVE LAYERS ON COPPER ELECTRODES IN SOME ALKALINE MEDIA
(1.Electrochemical Research Group, Shanghai Institute ofElectric Power, Shanghai200090, P. R. China;
2.Corrosion Prevention Center, East China University of Science and Technology, Shanghai200237, P. R. China;
3.Department of Chemistry, University of Alabama, Huntsville, AL35899, USA)
2.Corrosion Prevention Center, East China University of Science and Technology, Shanghai200237, P. R. China;
3.Department of Chemistry, University of Alabama, Huntsville, AL35899, USA)
Abstract: The electrochemical behavior of Cu electrodes in alkaline solutions with and without argon-gas purging was studied by cyclic voltammetry and the photocurrent response method. In Na2SO4 solution (pH 9.1), the electrode shows a p-type photoresponse initially, which changes to an n-type when pitting corrosion occurs, at potentials more positive than the critical breakdown potential. The cathodic photocurrent is much larger in stronger alkaline solutions, e. g.,0.1 mol/L KOH solution, reflecting a more porous structure of Cu2O layer on the electrode surface in strong alkaline solutions. Additionally, the cathodic current is larger in deaerated solutions than that in non-deaerated solutions. While the initiation of CuO formation on the electrode may not be obvious on the current-voltage curve, it can be obtained from the photocurrent-voltage curve where it corresponds to the onset of the decrease in the photocurrent on the positive potential scan.
Key words: copper electrode alkaline solutions passive layer photocurrent response cyclic voltammetry