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The influence of reduced graphene oxide on the pseudocapacitive properties of a conductive polymer layer for supercapacitor applications

With the rapidly expanding energy storage market there has been an increasing and urgent need for efficient and sustainable sources of energy. Supercapacitors are considered a promising candidate and an alternative to batteries because of their higher power density and longer cycle life. However, one of the major disadvantages of supercapacitors is the insufficient energy density, which has been the main drawback for the wide application expected. Today, supercapacitors development is focused on active materials that are required to provide both high power and high energy density [1]. Conductive polymers, such as poly(3, 4-ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) are attractive materials in terms of practical applications, especially in energy conversion and storage. They have excellent properties, including low cost, flexibility, and good electrical conductivity which results in a fast electrochemical redox reaction. However, due to their poor mechanical strength they have low cycling stability. To improve these properties different composites of conductive polymers and graphene have been synthesized by chemical or electrochemical polymerization [2]. In this work, a facile electrochemical method is introduced for incorporating graphene oxide (GO) into PEDOT and PPy layers in the presents of sodium dodecyl sulfate (SDS) as a supporting electrolyte. The presence of SDS can enhance not only the polymerization step but also the morphology and microstructure of the conductive polymer layer. The obtained composite layers were polarised at the potential of -1.4 V in 0.1 mol dm-3 KCl solution to reduce GO (rGO) within the polymer. rGO could significantly increase cycling stability and improve pseudocapacitive properties suitable for supercapacitors application. Morphological and structural properties of the obtained layers were characterized by means of scanning electron microscopy and UV/Vis spectroscopy. The obtained nanocomposite materials were used to assemble symmetric supercapacitors that were tested by cyclic voltammetry and electrochemical impedance spectroscopy methods. The stability of the supercapacitors was determined by their charging/discharging at a constant current during 1000 cycles, and the specific capacitance, energy, and power were calculated. The obtained results revealed that PEDOT/rGO and PPy/rGO composites have better pseudocapacitive properties than pure PEDOT and PPy, or the unreduced composite layer.

supercapacitors, reduced graphene oxide, poly(3, 4-ethylenedioxythiophene), polypyrrole

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