The preparation of conducting polymer aerogels is an effective strategy to produce innovative materials with enhanced physicochemical properties. Herein, polypyrrole (PPy) aerogels were oxidatively prepared in the presence of tannic acid (TA) with different concentrations (2.5, 5, and 10% mole ratio to pyrrole monomer) under freezing conditions. Nanofibrillated cellulose (NFC) was added during the PPy/TA synthesis to enhance mechanical stability. The effect of TA concentration on the aerogels' morphology, conductivity, thermal stability, and adsorption capacity was investigated. The conductivity of 9.6 ± 1.7 S cm-1 was achieved for PPy/TA prepared with 2.5% TA, which decreased to 0.07 ± 0.01 S cm-1 when 10% TA was used. PPy/TA aerogels have shown high efficacy in removing Cr(VI) ions from aqueous solutions. Adsorption experiments revealed that all the aerogels follow pseudo-second-order kinetics. PPy/TA prepared with NFC has a maximum adsorption capacity of 549.5 mg g-1.

• Keywords
• adsorption, aerogels, hexavalent chromium ions, polypyrrole, tannic acid,
• Publication type
• Journal Article MeSH

The polymerization of pyrrole in the frozen state with the presence of organic dyes (methyl orange (MO) and Acid Blue 25 (AB)) has proven to produce polypyrrole (PPy) nanostructures. Herein, we explore the electrochemical properties of PPy prepared under frozen-state conditions (-24 °C) with and without the presence of organic dyes. The electroactivity of PPy prepared with MO and AB significantly increased in all electrolytic media with a capacitance higher than this of the PPy prepared at room temperature. The highest capacitance (1914 F g-1) was obtained for PPy-MO in 0.2 M HCl solution. The impedance spectra of PPy showed a decrease in charge transfer resistance when the dyes were present. This indicates a conductivity increase of PPy. Improved electrochemical stability was observed for PPy, PPy-MO, and PPy-AB prepared at -24 °C, wherein a steady gain of capacitance was maintained during 5000 potential cycling. In addition, a PPy-based supercapacitor device was fabricated to demonstrate the energy storage characteristics of PPy, where it showed good capacitive behavior and stability. Overall, frozen-state polymerized PPy posed an impressive capacitive performance for flexible supercapacitors.

• Keywords
• Acid Blue 25, frozen-state polymerization, methyl orange, polypyrrole, supercapacitors,
• Publication type
• Journal Article MeSH