Study of copper sulfide film formation by voltammetry combined with electrochemical quartz crystal microgravimetry/coulometry and optical spectroscopy

This paper describes a study of copper sulfide film formation at copper anodes in sulfide-containing aqueous NaOH media. Voltammetry along with combined electrochemical quartz crystal microgravimetry (EQCM)/coulometry showed the formation of an initial Cu2S (chalcocite) phase. Further oxidation resulted in a nonstoichiometric overlayer culminating in a surface that was CuS (covellite) in composition. The EQCM data also revealed incipient dissolution of the copper surface in the alkaline sulfide media as Cu(I) species. Chemical sulfidization of the copper surface is also shown to be an important film formation pathway. Complementary spectroscopic data were obtained in situ by visible reflectance spectroscopy and laser Raman spectroscopy. Ex situ analysis of the copper sulfide layer composition by X-ray photoelectron spectroscopy is also presented.