Analysis of photocurrents and capacitance at TiO2 nanotubes/polyaniline hybrid composites synthetized through electroreduction of aryldiazonium salt

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.