A simple method for the fabrication of WO3 films with electrochromic and photocatalytic properties

This work proposes a simple and inexpensive method for the deposition of WO3 films with electrochromic and photocatalytic properties. It consists of preparing a precursor solution of WO3 powder in H2O2, allowing the precursor to age for a period of 1 to 2months and then spraying it on an appropriate substrate. Changes in the crystallinity of the WO3 particles within the precursor were observed during aging. They were taken advantage of for the preparation of homogeneous WO3 films of optical quality. The films thus prepared are amorphous, stable, with good adherence on the substrate. They exhibit favorable electrochromic properties, such as a high Li ion diffusion coefficient (of about 5×10−10cm2/s) and reversible coloration with efficiencies of 132cm2/C at 389nm, 48.9cm2/C at 534nm and 52.4cm2/C at 800nm. These films were also used as photo-anodes for the photocatalytic degradation of methylene blue (MB) in a NaOH aqueous solution with promising results. Effective degradation of MB was observed with the lowest half-life time of 55min recorded for a NaOH concentration of 0.8M. •A simple method for the fabrication of WO3 films is proposed.•It comprises spray deposition of an aged precursor of WO3 dissolved in H2O2.•Aging alters the crystallinity of the WO3 particles, and leads to better films.•The WO3 films exhibit favorable electrochromic and photocatalytic properties.