Enhancement of gasochromic response to hydrogen of WO3 thin films by post-process modification and catalyst selection.

The gasochromic properties of WO 3 thin films deposited by electron beam evaporation were investigated, focusing on their structural, morphology and optical changes caused by heat treatment. Moreover, the influence of the thickness and type of catalyst on the gasochromic properties of WO 3 was examined. X-ray diffraction measurements revealed that WO 3 thin films annealed up to 473 K remained amorphous, whereas annealing at 673 K and above, initiated crystallization into a monoclinic structure. Gasochromic behaviour was observed in response to hydrogen exposure, with the most significant changes occurring in films annealed at 673 K with a thin adlayer of palladium catalyst. A gasochromic response of 1.84 was achieved for H 2 concentration as low as 25 ppm. The process of gasochromic colouration was correlated with the changes of free charge carrier concentration calculated based on Drude free electron theory. XPS analysis confirms WO 3 reduction under hydrogen exposure, validating proposed colouration mechanisms. These comprehensive findings offer insights into optimizing gasochromic thin films for various sensing applications. [Display omitted] • Thermal treatment at 673 K enhanced a gasochromic response of WO 3. • Type and thickness of catalyst influenced on gasochromic response of WO 3. • Very high gasochromic response of 1.84 for WO 3 was obtained for 25 ppm of H 2. • Free charge carrier concentration in WO 3 films increased after exposure to H 2. • XPS revealed that tungsten oxidation state decreased upon exposure to H 2. [ABSTRACT FROM AUTHOR]