Cu-doped W18O49 nanowire reticular films for electrochromic supercapacitors

The method of improving the electrochromic properties of tungsten oxide by doping has attracted great interest. In this study, we successfully fabricated nanostructured tungsten oxide with different copper doping concentrations by a solvothermal method using copper chloride dihydrate and tungsten hexachloride as precursors. We found that the area-specific capacitance of the films gradually increased with the increase in doping concentration. The products were characterized by x-ray photoelectron spectroscopy, x-ray diffraction, scanning electron microscopy, cyclic voltammetry, and chronoamperometry. The results show that the films we fabricated are reticular structures composed of nanowires. The doping of copper can improve the electron conductivity and shorten the ion transmission distance, thus improving energy storage properties. When the doping concentration is 7% and the annealing temperature is 200 °C, the film had the largest surface capacitance of 17.89 mF/cm2 and the capacitance retention reached 58.23%.