Highly stable polypyrrole film prepared by unipolar pulse electro-polymerization method as electrode for electrochemical supercapacitor

• Superstable PPy thin film was fabricated using a facile UPEP method.
• The growing PPy film was found to keep at an oxidized state during polymerization process.
• Ordered structure with reduced chain defects of PPy film was obtained.
• The PPy film exhibited an excellent cycling stability even in a neutral solution.

Polypyrrole (PPy) film was fabricated on platinum substrate by a facile unipolar pulse electro-polymerization (UPEP) method. Mechanism for the formation of highly stable PPy film was proposed based on the chronoamperogram obtained during the polymerization process. Structure, surface morphology and hydrophilic property of the PPy film prepared using either UPEP method or potentiostatic method (PM) were characterized by Fourier transfer infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and contact angle goniometer, respectively. Electrochemical performances of PPy films prepared by UPEP and PM were compared using cyclic voltammetry (CV), galvanostatic charge/discharge tests and electrochemical impedance spectroscopy (EIS) in 1.0 M of KCl solution. It is found that the PPy film prepared by UPEP method under the conditions of ultra short on-time pulse (10 ms) and low temperature (10.0 °C) showed an ordered structure with reduced chain defects and exhibited high specific capacitance and excellent cycling stability in neutral solution. The capacitance of such a PPy film electrode retained 93.6% of its initial value even after 50,000 charge/discharge cycles. The specific capacitance of the UPEP PPy film reached 406.0 F g−1 at a scan rate of 5 mV s−1 when temperature, pulse potential, pulse time ratio (ton/toff) and pulse cycles were 10.0 °C, 0.7 V, 10 ms/100 ms and 12,000, respectively.

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