Poly(3-methylthiophene)/MnO2 composite electrodes as electrochemical capacitors

Composite electrodes prepared by electrodeposition of manganese oxide on titanium substrates modified with poly(3-methylthiophene) (PMeT) were investigated and compared with Ti/MnO2 electrodes. The polymer films were prepared by galvanostatic deposition at 2 mA cm−2 with different deposition charges (250 and 1500 mC cm−2). The electrodes were characterized by cyclic voltammetry in 1 mol L−1 Na2SO4 and by scanning electron microscopy. The results show a very significant improvement in the specific capacitance of the oxide due the presence of the polymer coating. For Ti/MnO2 the specific capacitance was of 122 F g−1, while Ti/PMeT250/MnO2 and Ti/PMeT1500/MnO2 displayed values of 218 and 66 F g−1, respectively. If only oxide mass is considered, the capacitances of the composite electrode increases to 381 and 153 F g−1, respectively. The micrographs of samples show that the polymer coating leads to very significant changes in the morphology of the oxide deposit, which in consequence, generate the improvement observed in the charge storage property.