Electropolymerized Polyaniline Stabilized Tungsten Oxide Nanocomposite Films: Electrochromic Behavior and Electrochemical Energy Storage

Polyainline (PANI)/tungsten oxide (WO3) nanocomposite films were fabricated by electropolymerization of aniline monomers onto WO3 coated indium tin oxide (ITO) glass slides, which were prepared by spin coating technique and followed by annealing at 500 degrees C for 2h. The morphology and crystalline structure of the composite films were studied using Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results confirm chemical interactions between the polymer matrix and the WO3 particles and reveal a well crystallized PANI/WO3 nanocomposite structure. The optical properties and electrochemical capacitive behaviors of the composite films for electrochromic (EC) and energy storage devices applications were investigated using spectroelectrocheinistiy (SEC), cyclic voltammetry (CV) and galvanostatic charge-discharge measurements. The composite films show dual electrochromism at both positive and negative potentials arising from PANI and WO3, respectively. A coloration efficiency of 98.4 cm(2) C-1 was obtained for the composite film, which was much higher, than that of WO3 (36.3 cm(2) C-1) and PANI (50.0 cm(2) C-1) thin film. An areal capacitance of 0.025 F cm(-2). thatis comparable to that of pure PANI (0.075 F, cm(-2)) is derived from CV at a scan rate of 5 mV/s with a broader working potential window of 1.3 V. The cyclic stability studies reveal that the composite films exhibit much more enhanced durability and-retain significant charge storage or discharge capacity after 1000 charge-discharge cycles. However, pure PANI loses most of the charge storage or discharge capacity after 350 cycles. The chemical bonding between PANI matrix and WO3 particles is believed to play an important role in enhancing the stability of the nanocomposite film.