Carbon xerogels (CXs) with three-dimensional (3D) structure, unusual surface, physical, electrical and mechanical properties and their electrically conductive polymer polypyrrole (PPy) composites were synthesized as electrode materials for supercapacitors. The effect of different resorcinol/formaldehyde (R/C) ratios, whether solvent exchange with or without acetone and polypyrrole addition on the physicochemical (FTIR, XRD, BET, SEM and TGA) and electrochemical properties (CV, 1000 cycles) of the synthesized materials were investigated. It was observed that the R/C ratio and the solvent exchange process prior to drying affect the specific surface areas and the pore size distributions, thereby positively affecting the specific capacitance. PPy film thickness was observed to be effective in the specific capacitance of the electrode in PPy composite synthesis. Among the synthesized materials, the highest specific capacitance values belong to polypyrrole/carbon xerogel composites. As a result of the analysis and calculations, it was found that the highest specific capacitance belongs to CX2/PPy composite with 599 Fg− 1 at 5 mVs− 1. CX2/PPy composite has been found to have a capacitance retention rate of 80.30% at the end of 1000 cycles.

In this work, iron oxide (Fe3O4) nanoparticles were deposited on multi-walled carbon nanotubes (MWNTs) by a simple chemical coprecipitation method and Fe3O4-decorated MWNTs (Fe-MWNTs)/polypyrrole (PPy) nanocomposites (Fe-MWNTs/PPy) were prepared by oxidation polymerization. The effect of the PPy on the electrochemical properties of the Fe-MWNTs was investigated. The structures characteristics and surface properties of MWNTs, Fe-MWNTs, and Fe-MWNTs/PPy were characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The electrochemical performances of MWNTs, Fe-MWNTs, and Fe-MWNTs/PPy were determined by cyclic voltammetry and galvanostatic charge/discharge characteristics in a 1.0 M sodium sulfite electrolyte. The results showed that the Fe-MWNTs/PPy electrode had typical pseudo-capacitive behavior and a specific capacitance significantly greater than that of the Fe-MWNT electrode, indicating an enhanced electrochemical performance of the Fe-MWNTs/PPy due to their high electrical properties.

Polypyrrole (PPy)/multi-walled carbon nanotubes (MWCNTs) composites were prepared by in situ polymerization of pyrrole on the surface of MWCNTs templates to improve the ammonia gas sensing properties. PPy morphologies, formed on the surface of MWCNTs, were investigated by field emission scanning electron microscopy. The thermal stabilities of the PPy/MWCNTs composites were improved as the content of MWCNTs increased due to the higher thermal stability of the MWCNTs. PPy/MWCNTs composites showed synergistic effects in improving the ammonia gas sensing properties, attributed to the combination of efficient electron transfer between PPy/MWCNTs composites and ammonia gas, and the reproducible electrical resistance variation on PPy during the gas sensing process.