Analysis of photocurrent and capacitance of TiO2 nanotube–polyaniline hybrid composites synthesized through electroreduction of an aryldiazonium salt

Abstract

TiO₂ nanotube–polyaniline hybrid composites were synthesized by a multi-step electrochemical procedure as follows: (1) electrochemical oxidation of Ti foil to obtain TiO₂ ordered nanotubular electrodes, (2) functionalization of TiO₂ by electroreduction of 4-nitrobenzendiazonium salt, (3) electrochemical reduction of the nitro group to amine, (4) galvanostatic electropolymerization of aniline onto the surface of the aminophenyl-modified TiO₂ electrode. Samples were also prepared by direct electropolymerization of PANI on TiO₂ nanostructures without the deposition of 4-nitrobenzendiazonium as under-layer. Different times for the electropolymerization step were applied. The composite materials were morphologically and electrochemically characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance analysis. The improvement of the most relevant properties of the PANI–TiO₂ composites for their application as photocatalysts and as supercapacitors was checked.