Spectroelectrochemical and structural properties of electrochromic Co(Al) -oxide and Co(Al,Si) -oxide films prepared by the sol-gel route

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 1996-11, Vol.418 (1), p.53-66
• Main Authors: Švegl, F., Orel, B., Bukovec, P., Kalcher, K., Hutchins, M.G.
• Format: Article
• Language: English
• Subjects: Chemistry; Co(Al)-oxide; Co(Al,Si)-oxide; Electrochemistry; Exact sciences and technology; General and physical chemistry; Miscellaneous (electroosmosis, electrophoresis, electrochromism, electrocrystallization, ...); Sol-gel; Spectroelectrochemistry; Structural properties
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/S0022-0728(96)04851-6

New electrochromic spinel-type Co(Al)-oxide and Co(Al,Si)-oxide films exhibiting coloring/bleaching changes Δ T= T colored− T bleached = 75% − 25% = 50% (where T is transmittance) with a coloring efficiency of 22cm 2 C −1 were deposited by a dip-coating method from aqueous colloidal solutions made by thermal hydrolysis of Co(II)-acetate, Al(III)-sulphate, citric acid and 3-aminopropyltriethoxysilane precursors. The nanocomposite spinel structure of the films and powders was determined using X-ray diffraction, thermogravimetry, visible and infrared transmission and reflection-absorption spectroscopy performed at near-grazing incidence angle conditions (80°) using p-polarized light. The existence of spinel lattice modes in the IR spectra of cycled films proved that the spinel structure of Co(Al,Si)-oxide films is preserved at least on the scale of short-range interactions detected with IR spectroscopy. In addition to this, sulphate (SO 4 2−) ions are retained in the structure of cycled films heat-treated at 500 °C. The role of order-disorder transitions of sulphate ions present in cycled films is discussed with respect to their influence in enhancing the speed and degree of coloring/bleaching changes of electrochromic Co(Al,Si)-oxide spinel films.