Electrochemical properties of polyaniline composite electrodes prepared by in-situ polymerization in titanium dioxide dispersed aqueous solution

Polyaniline (PANI)/titanium dioxide (TiO2) composites were prepared by a chemical oxidation polymerization. The composites were prepared with various amount of TiO2 to find a relation between electrochemical properties of composites and compositions of TiO2 and PANI in the composites. PANI/TiO2 composites which had PANI as a shell and TiO2 as a core part of the composites were successfully synthesized. Fiber-like PANI was also observed within the composites. The synthesis was explained as two stages of polymerization. First stage is a polymerization reaction occurred by a strong oxidative potential of TiO2. Second stage is started by adding ammonium peroxydisulfate in reaction solution. Diameters of aggregations of the composites increased with the added amounts of TiO2. The composite prepared with 10 wt.% of TiO2 per aniline monomer weight showed the highest capacitance of 784 F g−1 among the prepared composites. But the composites prepared with excess amounts of TiO2 showed lower capacitance than the highest one. The lower capacitances of the composites prepared with excess amounts of TiO2 was considered as related with the diameters of the aggregations. The composites prepared with excess amounts of TiO2 had large diameters for the aggregations. The TiO2 particles in the core of composites that had large diameter are hard to participate in electrochemical reaction due to a long pathway from electrolyte to TiO2 core and a blocking effect by outer TiO2 particles.