American Chemical Society
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Cathodic Electrodeposition of Mixed Molybdenum Tungsten Oxides from Peroxo-polymolybdotungstate Solutions

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journal contribution
posted on 2006-12-05, 00:00 authored by Lilia Kondrachova, Benjamin P. Hahn, Ganesh Vijayaraghavan, Ryan D. Williams, Keith J. Stevenson
Mixed molybdenum tungsten trioxide films of varying stoichiometry (MoxW1-xO3, 0 < x < 1) were prepared by cathodic electrodeposition on indium tin oxide (ITO)-coated glass substrates from aqueous peroxo-polymolybdotungstate solutions. Electrochemical quartz crystal microbalance (EQCM), cyclic voltammetry, and chronocoulometry were used to gain insight into the electrodeposition mechanism. The compositional and structural properties were characterized for MoxW1-xO3 films deposited at intermediate potentials (−0.35 V vs Ag/AgCl) and sintered at 250 °C using energy-dispersive spectroscopy, X-ray diffraction, and Raman spectroscopy. These studies reveal that films consist of homogeneously mixed MoxW1-xO3, with an enriched Mo content ranging in composition from 0.4 < x < 0.7 depending upon the mol % Mo present in the deposition solution. Chronoamperometry and spectroelectrochemical measurements were conducted to estimate lithium ion diffusion coefficients and coloration efficiencies for the mixed metal oxide films in 1 M LiClO4/propylene carbonate. The subtle interplay between structural and compositional properties due to the uniform mixing of Mo and W oxide components shows that electrochromic and lithium ion transport properties are moderately enhanced relative to those of single-component WO3 and MoO3 and demonstrate improved structural stability over pure MoO3 polymorphs during electrochemical cycling.