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