New insight into the mechanism of cathodic electrodeposition of zinc oxide thin films onto vitreous carbon

• Published in: Electrochimica acta 2013-04, Vol.94, p.238-244
• Main Authors: Ait Ahmed, N., Eyraud, M., Hammache, H., Vacandio, F., Sam, S., Gabouze, N., Knauth, P., Pelzer, K., Djenizian, T.
• Format: Article
• Language: English
• Subjects: Carbon; Chemical Sciences; Cyclic voltametry; Deposition; Diffraction; Electrodeposition; Material chemistry; Nanorods; Nanowires; Nitrate solution; Reduction; Thin films; Zinc; Zinc oxide; ZnO deposition mechanism
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2013.01.103

► A new mechanism for ZnO formation on vitreous carbon is proposed in nitrate medium. ► At low potential, a ZnO layer is obtained by direct oxidation of bulk zinc by nitrate ions. ► At higher cathodic potential, ZnO is obtained by two parallel mechanisms. ► The nanostructured film obtained at −1.1V has a (002) texturation. In this study, the mechanism of zinc oxide (ZnO) electrodeposition from aqueous zinc nitrate solution at 70°C was investigated on vitreous carbon and bulk zinc electrodes using cyclic voltammetry experiments. The first widely accepted route corresponds to ZnO precipitation from Zn2+ and OH− produced by NO3− reduction; the second route, which is discussed in this article, is due to Zn2+ reduction into metallic Zn followed by its oxidation by nitrate ions. For this case, we demonstrate why Zn formation cannot be observed while Zn2+ reduction was detected. Structure and morphology of bulk deposits were investigated using X-ray diffraction and scanning electron microscopy. Thin films of well-oriented ZnO nanorods were grown on vitreous carbon from Zn(NO3)2 solution at low cathodic potential corresponding to that of zinc metal deposition. X-ray diffraction (XRD) measurements showed that the nanorods are crystalline and preferably grow along the (002) direction.