Polypyrrole (PPy) is one of the attractive conducting polymers that have been investigated as energy storage materials in devices like supercapacitors. Previously, we have reported a free-standing soft PPy membrane synthesized through interfacial polymerization in which methyl orange (MO) and ferric chloride were used as nano template and oxidant. In this work, we report that the presence of MO and the treatment of the PPy-MO membrane with sulfuric acid can dramatically increase the specific capacitance of the membrane. The properties of the membranes were evaluated using scanning electron microscope (SEM) for morphology, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) for chemistry, thermogravimetric analysis (TGA) for thermal stability, and cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) for electrochemical activity. It was found that the areal specific capacitance of the PPy membrane increased from 2226 mF/cm2 to 6417 mF/cm2 and the charge transfer resistivity decreased from about 17 Ω to 3 Ω between 10,000 and 0.1 Hz due to the presence of MO and the acid treatment. It is likely that the superposition effect of MO and acid treatment helped the charge transfer process and consequently enhanced the charge storage performance and specific capacitance of the PPy membrane.
Keywords: energy storage; interfacial polymerization; methyl orange; polypyrrole; sulfuric acid; supercapacitor.