Electrodeposition and pseudocapacitive properties of tungsten oxide/polyaniline composite

Composite films of tungsten oxide (WO₃) and polyaniline (PANI) have been electrodeposited by cyclic voltammetry in a mixed solution of aniline and precursor of tungsten oxide. Surface morphology and chemical composition of WO₃/PANI composite are characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The influence of H ₂O₂ on the electrodeposition of WO₃/PANI composite film is also investigated. Cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS) results show that WO₃/PANI composite film exhibit good pseudocapacitive performance over a wide potential range of -0.5 to 0.7 V vs. SCE with the specific capacitance of 168 F g^-1 at current density of 1.28 mA cm^-2 and energy density of 33.6 Wh kg^-1, which is 91% higher than that of similarly prepared PANI (17.6 Wh kg^-1). An asymmetric model capacitor using WO₃/PANI as negative and PANI as positive electrodes over voltage range of 1.2 V displays a specific capacitance of 48.6 F g^-1 and energy density of 9.72 Wh kg^-1 at the power density of 53 W kg^-1, which is two times higher than that of a symmetric capacitor modeled by using two PANI films as both positive and negative electrodes.