Composite WO3–TiO2 films prepared by pulsed electrodeposition: morphological aspects and electrochromic behavior

This study builds upon on an earlier communication from our group [Electrochem. Commun. 5 (2003) 220] that described the preparation, by pulsed cathodic electrodeposition, of WO3–TiO2 composite films over a wide compositional range. We focus here on the morphology of these composite oxide films as probed by scanning tunneling microscopy and their electrochromic behavior. It is shown that the progressive coloration of an initially transparent conducting oxide glass substrate, as a result of oxide film growth, offers a versatile spectroelectrochemical probe of the film electrosynthesis process itself. Finally, both the blue shift undergone by the absorption threshold of the oxide film (as a result of electron accumulation during the electrochromic process), and the coloration dynamics are favorably influenced by the presence of small amounts of TiO2 in the WO3 film.