A Simple Trick to Increase the Areal Specific Capacity of Polypyrrole Membrane: The Superposition Effect of Methyl Orange and Acid Treatment

Abstract

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.

Study of Chemical Polymerization of Polypyrrole with SDS Soft Template: Physical, Chemical, and Electrical Properties

“…For 0.01 M Py, the PPy sample was a combination of sheets and particles, with an During chemical polymerization, SDS was a bifunctional substance, acting as a soft template in forming PPy sheets and doping PPy for enhanced electrical conductivity. 38,39 In its soft template role, SDS established micelles at a concentration higher than its CMC of 0.008 M. The micelles became compact when the SDS concentration increased, yielding micellar lamellae or hexagons at an extra-high SDS concentration. 42,48 In the presence of water, the SDS molecules turn their hydrophilic parts toward water, hiding hydrophobic branches inside the micelles.…”

“…In the second operation, the effects of SDS concentration (0.01 to 0.30 M) on PPy formation at constant Py concentration (0.04 M) were studied. The selected range of SDS concentration exceeded the critical micelle concentration (CMC) of 0.008 M, , signaling that SDS micelles were formed. As the SDS concentration increased from 0.01 to 0.10 M, the average particle size of PPy dropped from 253.90 to 100.10 nm, corresponding to PdI values of 0.39 and 0.16.…”

“…During chemical polymerization, SDS was a bifunctional substance, acting as a soft template in forming PPy sheets and doping PPy for enhanced electrical conductivity. , In its soft template role, SDS established micelles at a concentration higher than its CMC of 0.008 M. The micelles became compact when the SDS concentration increased, yielding micellar lamellae or hexagons at an extra-high SDS concentration. , In the presence of water, the SDS molecules turn their hydrophilic parts toward water, hiding hydrophobic branches inside the micelles. The Py monomer is a hydrophobic substance (Log P = 0.75, where P is the partition coefficient between octanol and water), and it could be surrounded by SDS, allowing the hydrogen in the Py to interact with the hydrophobic branches in SDS.…”

“…These results support our finding that utilization of SDS, with proper amounts of Py and APS, in the chemical polymerization of PPy can effectively enhance PPy conductivity. , The resistance of PPy decreased from 1.50 GΩ to 5.29 MΩ when the SDS concentration increased from 0.01 to 0.20 M (Figure b). In this study, we observed a substantial alteration in the PPy resistance when the SDS concentration was at or below 0.04 M, which is close to the CMC values (0.008 to 0.0083 M). , When the SDS content was low, PPy acquired irregular shapes (correlating with a high PdI, 0.39), yielding poor adhesion and electrical contacts between each PPy particle. The phenomenon led to a high resistance for the PPy chemiresistive device .…”

“…Template-assisted polymerization is a well-known technique that utilizes soft or hard templates to form a certain physical morphology of a polymer. The technique was demonstrated in a synthesis of various PPy nanostructures, including nanospheres, , nanotubes or nanowires, − nanorings, and nanosheets. − In a hard template technique, a solid mold was applied for polymerization, providing the physical morphology that the polymer grew in and subsequently adopted. The soft template, on the other hand, exercised the concept of self-assembly polymerization, relying on a unique reaction or interaction between a monomer and a soft template substance in attaining a designed physical morphology.…”