Electrochromism of phosphotungstic acid incorporated in titanium alkoxide xerogel films

U. Lavrencic Stangar; Boris Orel; Michael G. Hutchins

doi:10.1117/12.185425

9 September 1994 Electrochromism of phosphotungstic acid incorporated in titanium alkoxide xerogel films

U. Lavrencic Stangar, Boris Orel, Michael G. Hutchins

Proceedings Volume 2255, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII; (1994) https://doi.org/10.1117/12.185425
Event: Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII, 1994, Freiburg, Germany

Abstract

Electrochromic-ion conductive gels ((sigma) equals 1.7 X 10^-4 S/cm) and thin solid films composed of phosphotungstic acid (PWA) incorporated in titanium oxide xerogel (PWA/Ti equals 0.07) were made via the 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 HClO₄ 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/cm², giving rise to H_xPW₁₂^y+O₄₀^3- species with x equals 4.7 and y equals 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 vW-O_c-W and inter vW-O_b-W vibrations of the Keggin's ions while the vW-O_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 PSA/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 / H₃PO₄ doped polyvinyl alcohol (PVA) / Sb:SnO₂ configuration.

Citation Download Citation

U. Lavrencic Stangar, Boris Orel, and Michael G. Hutchins "Electrochromism of phosphotungstic acid incorporated in titanium alkoxide xerogel films", Proc. SPIE 2255, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII, (9 September 1994); https://doi.org/10.1117/12.185425

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