Academic literature on the topic 'Graphene-polypyrrole composite'

Graphene–polypyrrole hollow sphere composite was synthesized for the first time via Pickering emulsion polymerization using graphene oxide as Pickering stabilizer. It was found that polypyrrole and graphene were well hybrid and all graphene–polypyrrole composites had a uniform hollow sphere structure, whose diameters gradually decreased as the pyrrole content decreased. The electrochemical properties of the composites as supercapacitor electrode were investigated. The test results displayed that the specific capacitance of the optimal ratio of composite could reach 238[Formula: see text]F/g at a current density of 1[Formula: see text]A/g, and a 90.7% capacitance retention could be achieved after 1500 cycles, which was a significant improvement compared with the 62.2% retention of pure polypyrrole.

Recently, non-magnetic composites acting as microwave absorbing materials are gaining more attention due to their unique advantages. In this work, polypyrrole@reduced graphene oxide@liquid metal (PGL) composites were successfully prepared through a simple approach as efficient microwave absorbing materials. The impedance matching performance of the composite was accurately adjusted by controlling the amount of graphene oxide (GO) and polypyrrole layer. The optimum PGL composite obtained a reflection loss of −46.81 dB at a low frequency of 2.17 GHz. This method provides a reference path in liquid metal-based non-magnetic microwave absorbing materials.

Polypyrrole/Graphene oxide composite material (PPy/GO) was synthesized using an in-situ chemical polymerization method. The formation of composite had been shown by the analysis of Fourier transfer of infrared spectroscopy and X-ray diffraction data. Scanning electron and transmission electron microscopy clearly showed sheet-like layered structure of graphite oxide surrounded by polypyrrole. Electrochemical properties were characterized by electrochemical station. We demonstrated the intercalation of conducting polypyrrole into the graphite sheets, and that as electrodes for supercapacitor, the PPy/GO composites (GO0.54) with PPy to GO mass ratio of 5:3 showed a competitive capacitance of 337 F g-1 at a scan rate of 2 mV s-1 than that of PPy alone. Given the electrical and electrochemical properties, we prospect that the PPy/GO composites should find applications in supercapacitors.

High conductive and polymer composite has good electrical, mechanical and electrochemical properties which is a scalable, multi-functional composite material. It is widely used in electric vehicles, power storage and military fields. This article treats graphene as the working electrode self-supporting film and prepares the structures of the reduction of graphene-polypyrrole-Sulfonated graphene three-layer composite membrane using Polypyrrole electrochemical deposition method. From the electricity microscope, we can observe that the composite film have a closely structure which improves the electrical conductivity and mechanical properties of highly conductive polymer material. Finally, this paper studies the electrical properties of the composite film by the way of electrical experiment. From the experiment, we can conclude that in the voltage driver of 1V, the composite film has a better driving performance which can reach a rate of 198 / s. Its cycle life is up to 8000 times. This provides a new method for preparation and study of graphene conductive polymer composite.

Polypyrrole/graphene oxide (PPyGO) composite was synthesized through in-situ emulsion oxidative polymerization method. The composite was simultaneously doped with dodecylbenzenesulphonic acid doped (DBSA). The reaction parameters were optimized in such a way to get the composite with best possible properties. Thus, the resulting composite showed enhanced conductivity that is 73 S/cm compared to DBSA doped polypyrrole (4.18 S/cm) and graphene oxide (0.57 S/cm). As, conductivity is very important characteristic for practical application of polymeric materials, so, this material with enhanced properties can be used for multiple purposes. It was further characterized through Fourier Transform infrared spectroscopy, X-Ray Diffraction Analysis, Scanning Electron Microscopy and Thermogravimetric Analysis, which showed the successful synthesis of the composite.

In this study, the electrical properties of graphene–polypyrrole (graphene-PPy) nanocomposites were thoroughly investigated. A numerical model, based on the Simmons and McCullough equations, in conjunction with the Monte Carlo simulation approach, was developed and used to analyze the effects of the thickness of the PPy, aspect ratio diameter of graphene nanorods, and graphene intrinsic conductivity on the transport of electrons in graphene–PPy–graphene regions. The tunneling resistance is a critical factor determining the transport of electrons in composite devices. The junction capacitance of the composite was predicted. A composite with a large insulation thickness led to a poor electrochemical electrode. The dependence of the electrical conductivity of the composite on the volume fraction of the filler was studied. The results of the developed model are consistent with the percolation theory and measurement results reported in literature. The formulations presented in this study can be used for optimization, prediction, and design of polymer composite electrical properties.

Conductive polymers (CPs) have potential application to commercial energy storage because of their high electrochemical activity and low cost. However, an obstacle in developing CP-based supercapacitors is the degradation in their capacitance during the charge-discharge process that leads to poor rate performance. This study fabricates layers of a high-performance self-assembled polypyrrole/reduced graphene oxide (PPY/RGO) composite material on a carbon cloth through electrochemical deposition. The layered graphene improved the electrochemical properties of PPY. Carbon fiber rods were coated with the PPY/RGO composite layer, the thickness of which depends on the deposition time. Adequate capacitive behaviors were achieved by using 16 layers of polypyrrole/reduced graphene oxide, with a specific capacitance of 490 F g−1 (0.6 A g−1) and good rate performance. The results here provide a novel means of preparing graphene-based nanocomposites films for a variety of functions. A symmetric device was subsequently assembled by using electrodes featuring 16 layers of the polypyrrole/reduced graphene oxide composite. It yielded a specific capacitance of 205 F g−1 and a high energy density of 16.4 Wh kg−1. It also exhibited good cycle stability, with a capacitance retention rate of 85% for 5,000 cycles.

A novel sulfur/polypyrrole/graphene nanosheet composite (S/PPy/GNS) was synthesized and investigated as a promising cathode material. This ternary composite was prepared via in situ polymerization of pyrrole monomer with nanosulfur and GNS aqueous suspension followed by heat-treatment. Scanning electronic microscopy observation revealed the formation of a highly porous structure consisting sulfur and polypyrrole coating on the GNS surface. In this composite, GNS works as nanocurrent collector and enhances the conductivity of the composite, and polypyrrole with its high adhesion ability to GNS could act as a binder to connect sulfur and GNS. The resulting S/PPy/GNS composite cathode exhibits high and stable specific discharge capacities of 991 mAh g-1 after 50 cycles at 0.1 C and good rate capability.

碩士
國立雲林科技大學
化學工程與材料工程系
105
The aim of this study is to investigate use polystyrene sphere as template for the preparation of reduced graphene oxide (RGO)/polypyrrole (PPy) hollow sphere nanocomposite electrode materials applied of supercapacitor electrode. Firstly, the preparation parameters of the polystyrene sphere as template substrate, including monomer / initiator ratio, stabilizer, solvent ratio, stirring speed, etc, prepared of polystyrene nano-sphere for the average particle size is 330 nm and the P.I. value is 0.167, to do the most suitable sulfonation. Furthermore, by the pyrrole monomer and initiator mole ratio to oxidation polymerization coating on the sulfonated polystyrene sphere. Finally, the polypyrrole hollow sphere (PPy-HS) is formed by solvent removal. In the second stage, after by the modified Hummer's method to prepared to the graphene oxide (GO), by the three different processes (P-I, P-II, P-III, respectively) to prepared to reduced graphene oxide/ polypyrrole hollow sphere composites to investigate its capacitance characteristics. P-I was prepared by compound GO and PPy-HS and used the reducing agent HI / AcOH at low temperature reducing GO to RGO; P-II was prepared by reducing GO to RGO at the same conditions and then RGO And PPy-HS compound; P-III made using the same procedure with PI, the only difference is that the aforementioned polystyrene sphere template is removed after compound. Experimental found that RGO@PPy-HS prepared by Process P-I the two-step synthesis method A had better capacitance properties. The RGO3@PPy7-HS (GO: Py = 3: 7 ) has a specific capacitance of 574 (F / g), and RGO1@PPy10-HS has a specific capacitance as high as 607 (F / g) at the 5 mV / s scan rate, and the cycle life of the former is 135% after 1000 turns.

The mounting concern for renewable energies from ecologically conscious alternatives is growing in parallel with the demand for portable energy storage devices, fuelling research in the fields of electrochemical energy storage technologies. The supercapacitor, also known as electrochemical capacitor, is an energy storage device possessing a near infinite life-cycle and high power density recognized to store energy in an electrostatic double-layer, or through a pseudocapacitance mechanism as a result of an applied potential. The power density of supercapacitors far exceeds that of batteries with an ability to charge and discharge stored energy within seconds. Supercapacitors compliment this characteristic very well with a cycle life in excess of 106 cycles of deep discharge within a wide operational temperature range, and generally require no further maintenance upon integration. Conscientious of environmental standards, these devices are also recyclable. Electrochemical capacitors are currently a promising candidate to assist in addressing energy storage concerns, particularly in hybridized energy storage systems where batteries and supercapacitors compliment each other’s strengths; however specific challenges must be addressed to realize their potential. In order to further build upon the range of supercapacitors for future market applications, advancements made in nanomaterial research and design are expected to continue the materials development trend with a goal to improve the energy density through the development of a cost-efficient and correspondingly plentiful material. However, it is important to note that the characteristic power performance and exceptional life-cycle should be preserved alongside these efforts to maintain their niche as a power device, and not simply develop an alternative to the average battery. It is with this clear objective that this thesis presents research on an emerging carbon material derived from an abundant precursor, where the investigations focus on its potential to achieve high energy and power density, stability and integration with other electroactive materials. Activated carbons have been the dominant carbon material used in electric double-layer capacitors since their inception in the early 1970s. Despite a wide range of carbon precursors and activation methods available for the generation of high surface area carbons, difficulties remain in controlling the pore size distribution, pore shape and an interconnected pore structure to achieve a high energy density. These factors have restricted the market growth for supercapacitors in terms of the price per unit of energy storage. Activation procedures and subsequent processes for these materials can also be energy intensive (i.e. high temperatures) or environmentally unfriendly, thus the challenge remains in fabricating an inexpensive high surface-area electroactive material with favourable physical properties from a source available in abundance. Double-layer capacitive materials researched to replace active carbons generally require properties that include: high, accessible surface-area; good electrical conductivity; a pore size distribution that includes mesopore and micropore; structural stability; and possibly functional groups that lend to energy storage through pseudocapacitive mechanisms. Templated, fibrous and aerogel carbons offer an alternative to activated carbons; however the drawbacks to these materials can include difficult preparation procedures or deficient physical properties with respect to those listed above. In recent years nanostructured carbon materials possessing favourable properties have also contributed to the field. Graphene nanoplatelet (GNP) and carbon nanotube (CNT) are nanostructured materials that are being progressively explored for suitable development as supercapacitor electrodes. As carbon lattice structured materials either in the form of a 2-dimensional sheet or rolled into a cylinder both of these materials possess unique properties desirable in for electrode development. In the proceeding report, GNPs are investigated as a primary material for the synthesis of electrodes in both a pure and composite form. Three projects are presented herein that emphasize the suitability of GNP as a singular carbon electrode material as well as a structural substrate for additional electroactive materials. Investigation in these projects focuses on the electrochemical activity of the materials for supercapacitor devices, and elucidation of the physical factors which contribute towards the observed capacitance. An initial study of the GNPs investigates their distinct capacitive ability as an electric double-layer material for thin-film applications. The high electrically conductivity and sheet-like structure of GNPs supported the fabrication of flexible and transparent films with a thickness ranging from 25 to 100 nm. The thinnest film fabricated (25 nm) yielded a high specific capacitance from preliminary evaluation with a notable high energy and power density. Furthermore, fast charging capabilities were observed from the GNP thin film electrodes. The second study examines the use of CNT entanglements dispersed between GNP to increase the active surface area and reduce contact resistances with thin-film electrodes. Through the use MWNT/GNP and SWNT/GNP composites it was determined that tube aspect ratio influences the resulting capacitive performance, with the formation of micropores in SWNT/GNP yielding favourable results as a composite EDLC. The third study utilizes electrically conducting polypyrrole (PPy) deposited onto a GNP film through pulse electrodeposition for use as a supercapacitor electrode. Total pulse deposition times were evaluated in terms of their corresponding improvements to the specific capacitance, where an optimal deposition time was discovered. A significant increase to the total specific capacitance was observed through the integration PPy, with the majority charge storage being developed via psuedocapacitive redox mechanisms. A summary of the studies presented here centers on the development of GNP electrodes for application in high power supercapacitor devices. The potential use for GNP in both pure and composite electrode films is explored for electrochemical activity and capacitive capabilities, with corresponding physical characterization techniques performed to examine influential factors which contribute to the final results. The work emphasizes the suitability of GNP material for future investigations into their application as carbon or carbon composite electrodes in supercapacitor devices.