Abstract
WO3 is a widely studied material for electrochromic and photocatalytic applications. In the present study, WO3 nanoparticles with a controlled structure (monoclinic or hexagonal) were obtained by controlled thermal decomposition of hexagonal ammonium tungsten bronze in air at 500 °C and 600 °C, respectively. The formation, morphology, structure and composition of the as-prepared nanoparticles were studied by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX). The photocatalytic activity of the monoclinic and hexagonal WO3 nanoparticles was studied by decomposing methyl orange in aqueous solution under UV light irradiation. In order to study the electrochromic properties of the WO3 nanoparticles, as well to introduce them for self-cleaning photocatalytic surface applications, thin films were prepared from the WO3 particles together with a conductive polymer. For this, PEDOT:PSS was used, which gives excellent opportunities for obtaining transparent and conductive thin films, suitable for both electrochromic and photocatalytic applications. By spin-coating, transparent PEDOT:PSS/WO3 composite thin films were prepared, on which cyclic voltammetry measurements were performed, and the coloring and bleaching states were studied. Our initial results for the PEDOT:PSS/WO3 composite thin films are promising, suggesting that such composites, after further development, might be successfully used in electrochromic devices and photocatalysis.
Highlights
Tungsten trioxide (WO3) is one of the most studied inorganic materials with a wide potential of technological applications in fields like large scale electrochromic devices as displays, smart windows and optical switching coatings [1, 2]
The morphology of the prepared WO3 samples was studied by transmission electron microscopy (TEM) and scanning electron microscope (SEM)
Such structures are both beneficial for photocatalysis and electrochromism, as the open structure of the particle aggregates means a higher specific surface area, and for electrochromic applications it is generally better to apply particles with a smaller size, in order to increase the transparency in bleached mode
Summary
Tungsten trioxide (WO3) is one of the most studied inorganic materials with a wide potential of technological applications in fields like large scale electrochromic devices as displays, smart windows and optical switching coatings [1, 2]. We optimized the annealing conditions of hexagonal ammonium tungsten bronze, (NH4)xWO3-y (HATB), through previous thermal studies (TG/DTA) in order to obtain the WO3 samples with appropriate crystal structures and compositions [18]. We proposed that a thin film of conductive polymer, as PEDOT:PSS, with dispersed photocatalytic nanoparticles could be applied in photocatalysis.
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