Electropolymerization of Aniline onto Anodic WO3 Film: An Approach to Extend Polyaniline Electroactivity Beyond pH 7

Generally, the redox activity of polyaniline (PANI) can only be retained in acidic media at pH < 3. This high acidity requirement has been a large obstacle in many applications such as biosensor, marine antifouling, and anticorrosion. In this study, composite film systems of PANI and tungsten trioxide (WO3) were fabricated by the electropolymerization of aniline onto anodic WO3 film. For the first time, we found that the prepared PANI/WO3 film possesses excellent electrochemical activity and cycling stability in neutral solutions. The morphology and composition of the PANI/WO3 films were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), whereas their electroactivity was evaluated by cyclic voltammetry. Particularly, the long-term stability of their electroactivity upon cycling was investigated in detail. The good electroactivity and high redox stability of the PANI/WO3 films in neutral media can be ascribed to the intercalated H+ ions into WO3 film during electropolymerization of aniline. Moreover, the reduced electroactivity of the PANI/WO3 films can be recovered readily by cyclic voltammetry in an acidic solution. This study provides a new method to tune the electroactivity of PANI beyond pH 7 and makes PANI a promising candidate for biosensors.