Supercapacitive Behavior of Oxidative Chemical Vapor Deposited Polypyrrole on Carbon Fabric in Aqueous Electrolytes

Abstract

Supercapacitors are energy storage devices that rapidly store and release short-term energy due to their high-power density. However, achieving both high energy density and sufficient stability is challenging. Conducting polymers like polypyrrole (PPy) show promising supercapacitive behavior but suffer from volume shrinkage during charge storage, reducing their cycling stability. Combining PPy with flexible carbon materials offers a potential solution to mitigate this issue as long as there is good contact between them. We employed the oxidative chemical vapor deposition (oCVD) method to prepare supercapacitor electrodes by depositing a submicrometer-thick layer of PPy onto carbon fabric (CF). The resulting PPy film exhibits the quinoid structure with bipolarons as dominant charge carriers, forms uniform coatings, and retains the CF’s porosity. The electrodes were characterized using electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge measurements in different aqueous electrolytes (HCl, KCl, and KOH 1M), showing substantial differences in performance in the three media. Among these, KCl proved to be highly suitable for the PPy/CF electrode. Second, we investigated the effects of deposition time during oCVD on the supercapacitive performance of the electrode. Electrochemical testing revealed that extending the deposition time increases the coating thickness, electrical conductivity, and the areal capacitance of the electrode. Finally, we explored the applicability of the electrode in a symmetric supercapacitor device. The fabricated symmetric supercapacitor device exhibits ideal capacitive behavior, with a high rate capability (up to 500 mV/s) and a relatively high operational voltage (1 V).