Electrochromism in Anodically Formed Tungsten Oxide Films

Abstract

By anodization of tungsten in acid solutions, oxide films were obtained Whose compositio,n depended on the working temperature. In particular, the composition .of the films was WO~ at 25 ~ and 50~ but WO3 9 H20 at 70~ Studies of electrochromism in these films seem to show that the electro coloration occurs with different mechanisms according to the oxide chemical composition. For WO3 films the coloration is due to a simultaneous injection of electrons and H + ions with formation of hydrogen tungsten bronzes H=WO3. For W~ 9 H20 films the coloration could occur as a result of the injection of electrons and oxygen ion vacancies with formation of blue oxide hydrate WO~-= 9 H~O.

Anodic growth of nanoporous WO3 films: Morphology, photoelectrochemical response and photocatalytic activity for methylene blue and hexavalent chrome conversion

“…To date, many methods have been used to prepare WO 3 in the form of powders, thin films or colloids, including, for example: sol-gel chemistry [16,[21][22][23][24][25][26], thermal oxidation of tungsten [2,3,5], thermal or e-beam evaporation [27,28], sputtering [3,25,26,29,30] spray pyrolysis [31], pulsed laser deposition [32], and chemical vapor deposition [33]. As pointed out elsewhere [34,35], electrodeposition offers a simple, low-temperature route to thin film preparation and thus WO 3 thin films have been grown by anodic [36,37], and more recently, cathodic [38][39][40][41][42][43][44][45][46][47][48][49] deposition routes. It must be noted that these earlier studies using anodic electrodeposition [36,37] used conditions (e.g., modest deposition potentials) leading to the formation of thin, compact oxide films on the parent metal surface.…”

X-ray study and structure simulation of amorphous tungsten oxide

“…The studies of non-crystalline WO 3 ®lms obtained by various methods show that their electrochromic properties are essentially dependent on the conditions and the methods of their synthesis (Aleshina et al, 1982(Aleshina et al, , 1998Fillipchenko et al, 1980;Gorbunov et al, 1981;Shiojri & Migano, 1980;Olevskii et al, 1984;Falaras et al, 1984;Paola et al, 1978). We can assume that this effect is associated with a different short-range order of atomic arrangement.…”

Molecular Design and Synthesis of New Noncrystalline Solids

“…As explored in previous studies (33 ) higher the annealing temperature, the faster was the decay of coloration.…”