Bringing Conjugated Polymers and Oxide Nanoarchitectures into Intimate Contact: Light-Induced Electrodeposition of Polypyrrole and Polyaniline on Nanoporous WO₃ or TiO₂ Nanotube Array

This proof-of-concept study focuses on the photocatalytic electrodeposition of two conducting polymers, namely, polyaniline (PANI) and polypyrrole (PPy), in two different nanostructured inorganic semiconductor host matrices, namely, nanoporous tungsten trioxide and nanotubular titanium dioxide. Oxide semiconductor (WO₃ and TiO₂) films were initially electrosynthesized on tungsten and titanium foils, respectively, by anodization at different voltages in fluoride-containing aqueous media. The conjugated polymer was electrografted onto the entire surface of the photoexcited oxide semiconductor matrix using potentiostatic and potentiodynamic deposition methods. The crucial role of initial photoelectrochemical deposition, preceding the electrochemical polymerization step, was demonstrated. The photoelectrodeposited and electrodeposited hybrid samples were compared from both morphological and electrochemical perspectives. Importantly, through application of the methodology presented in this article, deposition of electroactive polymers can be achieved homogenously, on both macroscale and nanoscale dimensions. The morphology and structural properties of these assemblies were evaluated by FE-SEM, ATR FT-IR, and Raman spectroscopy, whereas their electroactivity was characterized by cyclic voltammetry

Electrodeposited Polyaniline in a Nanoporous WO₃ Matrix: An Organic/Inorganic Hybrid Exhibiting Both p- and n-Type Photoelectrochemical Activity

This study focuses on the electrodeposition of a conducting polymer such as polyaniline (PANI) into a tungsten trioxide nanoporous host framework. Nanoporous WO₃ films were initially electrosynthesized on tungsten foil by anodization at different voltages in a fluoride-containing medium. The PANI layer was electrografted onto the entire surface of the WO₃ using potentiodynamic electrodeposition in sulfuric acid electrolyte. The morphological features of oligomer/polymer formed in the nanoporous oxide template were monitored by field-emission scanning electron microscopy. Systematic changes in the morphology afforded insights into the evolution of the WO₃/PANI hybrid assembly. This assembly was subsequently characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and photoelectrochemical measurements. Photovoltammetric data indicated the complex behavior of the hybrid, featuring the properties of both of its components: namely, p-type behavior in the cathodic polarization regime and n-type behavior at the anodic end. Moreover, much higher cathodic photocurrents were observed for PANI in the hybrid configuration (compared to neat PANI itself), in which effective charge separation manifested in the shape of the photocurrent transients