Abstract:

This work is focused on the combination of two building-blocks, nanocrystalline TiO₂ particles and polyaniline conductive films (PAni). The preparation of new nanostructured composite materials, displaying electron- and proton-conductive properties, to be used for the fabrication of new and superior energy storage devices was envisaged. The semiconducting TiO₂ nanoparticles were obtained by means of a hydrothermal route. The PAni films were prepared on glassy carbon electrodes by electrochemical polymerization, under potential dynamic conditions. After characterization by X-ray diffraction, transmission electron microscopy or scanning electron microscopy and electrochemical techniques, the nanocrystalline particles were immobilized in the polymer matrix. The incorporation of the TiO₂ was achieved using two distinct approaches: during the polymer growth or by deposition over previously prepared PAni films. The results demonstrate that the PAni morphology depends on the experimental conditions used during the polymer growth. After TiO₂ immobilization, the best electrochemical response was obtained for the nanocomposite structure produced through the TiO₂ incorporation after the PAni film synthesis. The modified electrodes were structurally and morphologically characterized and their electro-catalytic activity towards the hydrogen evolution reaction was analyzed. A new electrochemical performance related with the oxidation of molecular hydrogen entrapped in the PAni-TiO₂ matrix was observed for the modified electrode after TiO₂ incorporation. This behavior can be directly associated with the synergetic combination of the TiO₂ and PAni, and is dependent on the amount of the semiconductor.