Electrochemical Storage in Zr-W Mixed Oxide Nanostructured Arrays

ZrO2-WO3 mixed-oxide nanostructures are created by anodizing a Zr-20 wt% W metal alloy at different potentials followed by annealing at various temperatures. The nanostructures are analyzed via SEM/TEM, X-ray diffraction, and XPS. Phases of h-WO3 and t-ZrW2O8 are found in both the as-anodized form and the annealed form. Also several electrochemical tests including cyclic voltammetry, EIS, and Mott-Schottky analysis are performed in electrolytes of different pHs. The maximum capacitance was determined to be ~45 mF/cm2. The defect concentration in the material was calculated by using the slopes of the Mott-Schottky curves. Finally, the mixed-oxide nanostructures were tested in a two-electrode apparatus which cycled the potential of the system between 0 V and 1 V. The charge and discharge times of the tests increased as cycling continued but the rate of increment changed with pH, annealing temperature, and, to a lesser degree, nanostructure.