Preparation And Electrochemical Performance Of PPy And Its Composites

Since the discovery of carbon nanotubes in 1991, conductive polymers such as nanotubes and nanofibres have aroused considerable interest within the scientific community due to their unique properties and technological application. Among the conducting polymers, polypyrrole (PPy) is a particularly promising material on account of its high energy storage capacity, good electrical conductivity, low cost, stability in air and its potential applications. Recently, micro-and nanotubes of PPy have been obtained using hard and soft templates. Hard templates have often been used in the polymer matrix to give precise control over size and shape, but the removal of a hard template requires harsh conditions, which not only complicates the fabrication process but may also damage the polymer matrix. From the aspect of safety and environmental hazards, the soft template is more suitable for preparing conductive polymeric micro-and nanotubes since conductive polymers can be grown in tubular form, and the soft template is easily removed following polymerization.The main content of this paper is introduced as follows:A hollow thorn-like polypyrrole (PPy) microtube structure (HTPMT) has been prepared byin situ chemical oxidation polymerization using Methyl Orange (MO) and sodium dodecylbenzene sulfonate (SDBS) as double soft templates, in which the MO and SDBS performed both as surfactant and dopant. The hierarchical structure of HTPMT formed in the presence of MO and SDBS was different from that of polypyrrole microtubes (PMT) or nanoparticles (PNP) using MO and SDBS separately. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that the morphology of the HTPMT had the appearance of thorns growing on the surface of the PMT. The TEM images of the MO and SDBS solutions revealed that PPy had polymerized on the surface of the end-closed MO tubes and in the vesicular SDBS micelles. Electrostatic attraction between the anionic SDBS micelles and cationic pyrrole radicals during the polymerization assisted the formation of the HTPMT. The HTPMT exhibited improved electrochemical performance and thermal stability compared with PMT or PNP, illustrating that the morphology and structure of the conductive polymer influenced the electrochemical performance of the electrode materials.Intrinsic polypyrrole (PPy) flexible film was successfully prepared by chemical oxidation with methyl orange (MO)-FeCl3 reactive self-degradable template method when the molar ratio of FeCl3 to monomer was 0.5. Scanning electron microscopy and transmission electron microscopy images show that the obtained PPy film was composed with different size of nanotubes which diameter is about 50～60 nm and length is 5-6 μm. Electrochemical performance of PPy film was evaluated using cyclic voltammetry, galvanostatic charge/discharge tests and electrochemical impedance spectroscopy in 1 M KCl aqueous electrolyte. The specific capacitance of the electrodes made by the PPy film is high up to 576 F/g at a current density of 0.2 A/g and retains 82% after 1000 charge-discharge processes at a current density of 3A/g. The excellent electrochemical performance provides wide application of PPy as supercapacitor materials.Well-defined polypyrrole/polyaniline (PPy/PANI) composite hollow nanospheres and nanoplatelets were prepared via in situ chemical oxidative polymerization of pyrrole and aniline in the presence of MO as the soft template, in which the MO was used as both the surfactant for the emulsion and the dopant for the produced composite. The effects of the initiator, such as the species and the amount on the morphology and electrochemical properties of the final PPy/PANI composite were investigated. It was found that the initiator exhibited an obvious influence on the morphology and electrochemical properties of the composite, such as the morphology was the hollow nanospheres with ammonium peroxodsulfate (APS) as the initiator, and the morphology was nanoplatelets with ferric chloride (FeCl3) as the initiator.Novel polypyrrole nanotubes/multi-walled carbon nanotubes (PPy/MWCNT) composites have been successfully synthesized via in situ chemical oxidation polymerization with methyl orange (MO) as soft template. Scanning electron microscopy and transmission electron microscopy images revealed that MWCNT intertwined with the PPy and PPy/MWCNT composites formed in water-ethanol solution. The obtained composites exhibited perfect electrochemical characteristic compared with PPy and MWCNT owing to the synergetic effect and the specific capacitance of the composites was strongly influenced by the mass ratio of pyrrole to MWCNT. According to the galvanostatic charge/discharge analysis, the specific capacitance of PPy/MWCNT composites is up to 352 F/g at a current density of 0.2 A/g in 1 M KCl solution, much higher than that of the PPy (178 F/g) and MWCNT (46 F/g), suggesting its potential application in supercapacitors.