The Preparation And Electrochemical Investigation Of Polythiophene-based Nanocomposites

Polythiophene and its derivatives are important energy storage materials for supercapacitor because of their low cost,high specific capacitance and rapid charge and discharge rate.By combining polythiophene derivatives with materials of high specific surface area and conductivity,a new type of composite electrode material for supercapacitor with better performance can be obtained.In this paper,three different polythiophene derivatives with-?OCH₂CH₂?₄OCH₃?PM4EOT?,-?OCH₂CH₂?₂N?CH₂CH₂OH?₂?PD2ET?and-?OCH₂CH₂?₄N?CH₂CH₂OH?₂?PD4ET?polar groups have been synthesized,and then combined with titanium dioxide?TiO₂?,carboxyl single-walled carbon nanotubes?SWNT-COOH?,graphene oxide?GO?to produce hybrid composite PM4EOT/TiO₂,and grafting composites PD2ET-g-SWNT,PD4ET-g-GO,respectively.Finally they were characterized by a series of mesurements.We also fabricated two symmetrical solid-state supercapacitors based on as-prepared grafting composites,and test their electrochemical properties.The obtained results of this paper are described as follows:1.The polythiophene with-?OCH₂CH₂?₄OCH₃ side group were combined with TiO₂ by different weight ratios to generate PM4EOT/TiO₂ nanocomposites via a facile in situ oxidative chemical polymerization.The morphology studied demonstrated that nanocomposites were of the core-shell structure with a particle size of approximately 30 nm and PM4EOT shell was of about 2-10 nm thickness.X-ray photoelectron spectroscopy?XPS?spectra proved that there was a new Ti-S interaction between the polymer and TiO₂ interface.The supercapacitive behaviors of the nanocomposites investigated by cyclic voltammetry?CV?,galvanostatic charge-discharge?GCD?and AC impedance measurements?EIS?collectively demonstrated that the prepared PM4EOT/TiO₂ nanocomposites at various ratio contents exhibite enhanced specific capacitance and cycling stability as compared to the two pristine components.The specific capacitance of PM4EOT/TiO₂ nanocomposite?1:1,weight ratio?was obtained up to117 F/g at a current density of 0.5 A/g,which is much higher than that of the pure PM4EOT?45F/g?and TiO₂?1.6 F/g?.In addition,the energy density of 15.4 Wh/kg and the power density of308 W/kg delivered by composite?1:1?capacitor were achieved at a current density of 0.5 A/g.2.The polythiophene with-?OCH₂CH₂?₂N?CH₂CH₂OH?₂ side group was chemically grafted to the SWNT-COOH?carboxylated carbon nanotubes?via esterification reaction to give a novel PD2ET-g-SWNT nanocomposite.Compared to the individual components of pure SWNT-COOH and PD2ET,there exists the synergistic effect of structure between SWNT and conductive polymer enhancing the electrochemical characteristics of the as synthesized PD2ET-g-SWNT in neutral media.The experimental results show that PD2ET-g-SWNT exhibits more superior electrochemical performance comparing with the PD2ET,SWNT-COOH and the physical mixture.The PD2ET-g-SWNT hybrid material possesses a specific capacitance as high as 399 F/g at 1 A/g,with energy and power densities of 35.44 Wh/kg and 400 W/kg,respectively.More interestingly,this hybrid can maintain 65%of its initial capacitance within3000 successive cycles,suggesting a superior electrochemical cyclic stability.A fully charged three-supercapacitor tandem device can light up a red light-emitting diode.3.A novel,neutral surfactant polythiophene with-?OCH₂CH₂?₄N?CH₂CH₂OH?₂ side group has been synthesized and used to covalently functionalize on GO nanosheets.The morphological details and elemental compositions analysis indicates that the PD4ET is successfully grafted to the edge of GO sheets with a few nanometers thickness.More significantly,PD4ET-g-GO electrode exhibit enhanced electrochemical performance with a maximum specific capacitance of 971?F/g at a current density of 1 A/g using a three-electrode system,which is much higher than that of each individual component and the physical mixture.High energy and power density achieved up to 66.11?Wh/kg and 350?W/kg and of 38.11?Wh/kg and 7000?W/kg,respectively.The cycling stability investigation showed that PD4ET-g-GO based capacitor can preserve 98%of its initial capacitance within 10000consecutive charge-discharge cycles,suggesting a good cycling stability for the composite electrodes.Furthermore,the fabricated solid-state supercapacitor device shows remarkable electrochemical performance,which can power the red LED diode in series connection.