The main purpose of this study is to improve the capacitive performance of reduced graphene oxide (RGO) coated cotton fabric (CF) by induction of pseudo-capacitive effects using simple and mass production methods. For this purpose, The CF was first coated by GO using the dipping-drying process as a simple, economical, and reproducible technique. Subsequently, via an environmentally friendly chemical reduction process with sodium dithionite, the GO on the CF surface was successfully converted to RGO. Three different electroless silver plating (ESP) methods were used to prepare the silver nanoparticles (AgNPs)/RGO/CF composite electrodes. The effect of the ESP method on morphological, structural, electrical, and electrochemical properties of the composite electrodes was eva‎luated. It was found that a tradeoff between the amount of deposited AgNPs, conductivity, and electrochemical performance is required to prepare the electrode with high energy storage ability. The simple and rapid ESP method, which was performed on the surface of RGO/CF at room temperature, achieved the electrode with the interconnected porous morphology providing the highest energy storage performance. This morphology provided easy electron transfer, short ion diffusion pathways, and increased penetration of the ions into the electrode materials, leading to improved electrochemical performance. This electrode showed high specific capacitance of 426±10 F/g in 0.5 M NaOH electrolyte during the CV cycles. Symmetric supercapacitor cell based on Ag/RGO/CF composite possessed outstanding cycle life (126% retention of initial specific capacitance after 1000 charge-discharge cycles) and good rate capability. All-solid-state flexible symmetric supercapacitor (ASFSSC) was assembled using this composite textile, which exhibited a high electrochemical performance stability under mechanical bending (89 % of initial capacitance retained after 1000 bending cycles) and delivered energy density as high as 34.6 Wh kg-1 (at a power density of 125 W kg-1). Polyaniline (PANI) is another pseudocapacitive material with high energy storage ability, which was used in this study to improve the electrochemical performance of RGO/CF electrode. The effect of monomer to oxidant ratio, oxidant type and de-doping process on morphological, structural, electrical, and electrochemical properties of the PANI/RGO/CF electrodes prepared by chemical polymerization method was investigated. The results showed that when the monomer to oxidant ratio is 1:0.5, oxidant is ammonium persulfate and polyaniline is fully doped, vertically polyaniline nanowires are synthesized on the RGO/CF electrode surface, resulting in the highest energy storage performance. ASFSSC based on this electrode exhibited a high specific capacitance of 367 F/g at a current density of 0.3 A/g and excellent electrochemical performance stability under mechanical bending (91.5 % of initial capacitance retained after 1000 bending cycles). This ASFSSC delivered high energy density of 35.9 Wh kg-1 (at a power density of 130.5 W kg-1). Also, through simple reaction of KOH with GO before coating on the surface of CF, the electrochemical performance of RGO/CF electrode significantly improved due to enhanced wettability and presence of residual oxygen-functional groups for pseudo-capacitance. The specific capacitance of KOH-treated RGO/CF was 164±7 F g-1 which is higher than that of RGO/CF (119±4 F g-1). The novel synthesized electrodes in this study can be promising candidates for the next-generation of wearable supercapacitors owing to their high flexibility and superior electrochemical performance.

مصطفي يوسفي، كيوان رئيسي

محمد ژياني

هژير بهرامي، علي اصغر انصافي، حسين فشندي