Construction of vertical arrayed three-dimension composite towards high coloration efficiency electrochromic film
Polyoxometalate-based electrochromic materials have been investigated for a long time due to the ability of excellent redox reversibility while give rise to colored mixed-valence state species. However, like traditional inorganic electrochromic materials, the response time and coloration efficiency still need to be improved. Herein, nanocomposite thin film constructed by composite mono-cerium substituted sandwich-type polyoxotungtate cluster K17[Ce(P2W17O61)2]·nH2O and TiO2 nanowires are prepared through electrodeposition method. Scanning electron microscopy (SEM), transmission electron microscope (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) are carried out to investigate the nanocomposite film’s surface morphology, structure, components and chemical properties. The electrochemical experiments and measurements are performed by combining in-situ UV-vis spectrophotometer together with electrochemical workstation. Compared with pure K17[Ce(P2W17O61)2]·nH2O modified film, the composite film exhibit high transmittance modulation (73.2% at -1V), fast response time (2.6s for coloration and 1.7s for bleaching), better cycle stability and especially improved coloration efficiency (111.3cm2·C-1). Combining the characterization and electrochemical test results, the obviously enhanced electrochromic properties could be attributed to the unique 3D structure of TiO2 nanowires substrate which could provide high specific surface area and fast reacting kinetic characteristic.