Ideally Capacitive Behavior and X-Ray Photoelectron Spectroscopy Characterization of Polypyrrole

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Abstract
Polypyrrole (PPy) films deposited by the galvanostatic method at 4°C with polymerization charges equal to/less than 1.0 C cm−2 were demonstrated to exhibit ideally capacitive characteristics with a high specific capacitance of 268 F g−1 for application to electrochemical supercapacitors. Influences of the polymerization temperature as well as the film thickness/coverage on the capacitive characteristics of PPy films were systematically investigated by cyclic voltammetry and the quasi-equilibrium charge-discharge technique. These influences were correlated with the structural properties examined by X-ray photoelectron spectroscopy. A positive shift in peak potentials of the redox transition occurring between 0 and 0.5 V on the positive sweeps of cyclic voltammetry curves and a gradual decrease in voltammetric currents of this peak were found to be proportional to the degree of degradation of PPy. The surface morphologies of PPy-coated electrodes with different growth charges were examined by a scanning electron microscope. © 2002 The Electrochemical Society. All rights reserved.