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 degrees 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.

Mixed molybdenum−tungsten oxides of varying stoichiometry (Mo x W1- x O3, 0 < x < 1) prepared by cathodic electrodeposition from aqueous peroxo-polymolybdotungstate solutions on indium tin oxide (ITO) coated glass substrates were evaluated by variable-angle spectroscopic ellipsometry (VASE) and transmission measurements from 200 to 1000 nm (1.24−6.2 eV). A Tauc−Lorentz dispersion model was used to determine the real and imaginary components of the complex refractive index for Mo x W1- x O3 films as a function of Mo fraction. The optical band gaps were also estimated from Tauc plots. The refractive index increased (2.07−2.20 at 800 nm) while the optical band gap decreased (3.38−2.95 eV) in a linear fashion for Mo x W1- x O3 films with increasing Mo fraction. These trends correlate chiefly with Mo-doping-induced changes in film structure and grain size as supported by X-ray diffraction measurements.

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A microscope-CCD setup has been developed as an analytical tool for the detection of diffraction from one-dimensional redox-active transition-metal oxide gratings prepared with a combination of microtransfer molding (microTM) and cathodic electrodeposition. The diffraction efficiencies (DE) of tungsten trioxide, WO3, and binary molybdenum-tungsten trioxide, Mo0.6W0.4O3, gratings were measured during Li+ insertion/deinsertion experiments performed with both cyclic voltammetry and chronoamperometry in 1 M LiClO4/propylene carbonate. The DE was evaluated in terms of the optical constants of the grating materials determined by spectroscopic ellipsometry (SE) measurements of Li+ insertion/deinsertion into unpatterned thin films. The effect of grating thickness and the amount of inserted charge on DE has been analyzed. The diffraction method is used to quantitatively estimate lithium ion diffusion coefficients of electrochemically active metal oxide gratings.