Voltammetry of chemically deposited Cu _x O electrochromic films, coated with ZnO or TiO₂ electrocatalyst layers

Abstract

Cu _x O is a known electrochromic material for solar light modulation applications. Cu _x O films were synthesized by chemical bath deposition (CBD) method from two aqueous solutions. The films contained the two oxide phases of copper, CuO and Cu₂O, established from the X-ray photoelectron spectroscopy (XPS) analysis. The scanning electron microscopy (SEM) scans of the Cu _x O film surface demonstrated that the films grew in round grains with average diameters of about 260, 470, and 620 nm, for the films grown upon 100,150, and 200 successive immersions, correspondingly. Cyclic voltammetry has been employed as a tool for examination of the reversible red-ox kinetics. It appeared that the grain size is an influential factor for the voltammetric parameter’s enhancement as the most distinct redox peaks were observed at the 470-nm grain size Cu _x O film. In order to enhance the electrochromic performance of the Cu _x O-based electrochromic device, two wide gap semiconductors (ZnO and TiO₂) were coated onto Cu _x O, assuming they reveal protection/catalyst character. Although the “morphology” of the voltammetric profile was found to be similar for the as-prepared and the coated Cu _x O films, the voltammetric intensity response apparently grew for the coated films. Furthermore, the results showed that the examined coatings catalyzed the electrochemical redox process, thereby boosting up the efficiency of the CuO ↔ Cu₂O reversible electrochemical conversion.