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

• 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.

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 2 months 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− 10 cm2/s) and reversible coloration with efficiencies of 132 cm2/C at 389 nm, 48.9 cm2/C at 534 nm and 52.4 cm2/C at 800 nm. 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 55 min recorded for a NaOH concentration of 0.8 M.