Electrochromism of phosphotungstic acid incorporated in titanium alkoxide xerogel films
Book
·
OSTI ID:194826
- National Inst. of Chemistry, Ljubljana (Slovenia)
- Oxford Brookes Univ. (United Kingdom)
Electrochromic-ion conductive gels ({sigma} = 1.7 {times} 10{sup {minus}4} S/cm) and thin solid films composed of phosphotungstic acid (PWA) incorporated in titanium oxide xerogel (PWA/Ti = 0.07) were made via the as studied sol-gel route by the dip-coating technique. The electrochromism of the as - deposited film was studied with the help of cyclic voltammetric (CV) measurements in HClO{sub 4} electrolyte, in-situ UV-VIS spectroelectrochemical measurements and ex-situ Near-Grazing Incidence Angle (NGIA) reflection spectroscopy. It was demonstrated that the color change from transparent to blue in the electrolytic cell is about 40 % and is accompanied with effective inserted charges up to 35 mC/cm{sup 2}, giving rise to H{sub x}PW{sub 12}{sup y+}O{sub 40}{sup 3{minus}} species with x = 4.7 and y = 5.6. Ex-situ NGIA FT-IR reflection measurements revealed that proton injection decreases the intensity of the longitudinal optical (LO) modes corresponding to the intra {nu}W-O{sub c}-W and inter {nu}W-O{sub b}-W vibrations of the Keggin`s ions while the {nu}W-O{sub d} modes remain unaffected. An intensity decrease of the LO modes of Ti-O vibrations was also detected in the ex-situ NGIA reflection spectra of cathodically colored pure Ti-xerogel films. It was found that the proton insertion process is accompanied by the hydroxylation of titanate ions, while no such an effect was noted for PWA/Ti and Ti xerogel films aged in water and the corresponding electrolytes without the applied potential. Electrochromic-ionic conductive properties of mixed PWA/Ti gels were demonstrated in a semi-liquid electrochromic cell (EC) with reflectance modulation and electrochromism of PWA/Ti solid films was shown by the in-situ UV-VIS transmittance measurements of an all-solid state device with PWA/Ti/H{sub 3}PO{sub 4} doped polyvinyl alcohol (PVA)/Sb:SnO{sub 2} configuration.
- OSTI ID:
- 194826
- Report Number(s):
- CONF-9404167--; ISBN 0-8194-1564-2
- Country of Publication:
- United States
- Language:
- English
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