Pure PPy Film Research Articles

Polypyrrole and La 1− xSr xMnO 3 (0≤ x ≤0.4) composite electrodes for electroreduction of oxygen in alkaline medium

Composite G/PPy/PPy(La 1− x Sr x MnO 3)/PPy electrodes made of the perovskite La 1− x Sr x MnO 3 embedded into a polypyrrole (PPy) layer, sandwiched between two pure PPy films, electrodeposited on a graphite support were investigated for electrocatalysis of the oxygen reduction reaction (ORR). PPy and PPy(La 1− x Sr x MnO 3) (0≤ x ≤0.4) successive layers have been obtained on polished and pretreated graphite electrodes following sequential electrodeposition technique. The electrolytes used in the electrodeposition process were Ar saturated 0.1 mol dm −3 pyrrole (Py) plus 0.05 mol dm −3 K 2SO 4 with and without containing a suspension of 8.33 g L −1 oxide powder. Films were characterized by XRD, SEM, linear sweep voltammetry, cyclic voltammetry (CV) and electrochemical impedance (EI) spectroscopy. Electrochemical investigations were carried out at pH 12 in a 0.5 mol dm −3 K 2SO 4 plus 5 mmol dm −3 KOH, under both oxygenated and deoxygenated conditions. Results indicate that the porosity of the PPy matrix is considerably enhanced in presence of oxide particles. Sr substitution is found to have little influence on the electrocatalytic activity of the composite electrode towards the ORR. However, the rate of oxygen reduction decreases with decreasing pH of the electrolyte from pH 12 to pH 6. It is noteworthy that in contrast to a non-composite electrode of the same oxide in film form, the composite electrode exhibits much better electrocatalytic activity for the ORR.

A novel one-pot synthesis of free standing Pd–PPy films: Observation of enhanced catalytic effect by Pd–Ppy layers

A novel one-pot method to synthesize palladium nanoparticles incorporated polypyrrole films (Pd–Ppy) is described. The films are homogeneous with palladium particles and can be peeled from the electrode surface as a free standing films. Novelty of this procedure is that the palladium particles are prepared and stabilized in presence of the surface-active dopant, dodecylbenzene sulphonic acid sodium salt (NaDBSA), and are incorporated in to the polymer matrix along with dopant during the growth of the film. It is observed that the incorporation of palladium is uniform and homogeneous. An unprecedented catalytic activity by these Pd–Ppy composite layers in enhancing the rate of polymer deposition is observed. The films also electrocatalyze the oxidation of hydrazine more effectively than do the pure Ppy films.

Controlling the nanostructure of electrochemically grown nanoporous composites of carbon nanotubes and conducting polymers

Nanoporous composite films of multi-walled carbon nanotubes (MWNTs) and either polypyrrole (PPy) or poly(3-methylthiophene) (P3MeT) were grown using an electrochemical polymerization technique in which the nanotubes and conducting polymer were deposited simultaneously. The concentration and dispersion of MWNTs in the polymerization electrolyte, in addition to any supporting electrolyte used, were found to have a significant effect on the thickness of polymer coated on each MWNT and hence the nanoporosity and MWNT loading in the films produced. It has been shown that in the absence of a supporting electrolyte, increasing the concentration of MWNTs in the polymerization electrolyte decreases the thickness of polymer coated on each MWNT. This relationship made it possible to minimize ionic diffusion distances and improve electrolyte access within the nanoporous MWNT-PPy films produced, thereby increasing their capacitance relative to similarly prepared pure PPy films.

An electrochemically synthesized conducting semi-IPN from polypyrrole and poly(vinyl alcohol)

The present work reports electrochemical synthesis of a semi-IPN (s-IPN) following electropolymerization of pyrrole from an aqueous medium within a crosslinked network of PVA. This combination resulted in a set of free standing and flexible films having high electrical conductivity and good environmental stability. Primarily three different types of samples were prepared by electropolymerization of pyrrole using a monomeric dopant (styrene sulfonate, SS), a polymeric dopant (poly(styrene sulfonate), PSS) and a crosslinked polymeric matrix (PVA-C). Considering the mechanical strength and flexibility of the resulting films, the PPy-PVA-C s-IPN was found to be the best one. Electropolymerization conditions were optimized by varying the concentrations of monomer and electrolytes and in some cases the solvent. Surface morphology (by SEM), thermal stability (through DSC and TGA) and electrical conductivity at different temperatures were studied and the s-IPN was found to possess improved electrical, thermal and environmental stability as compared to the pure PPy film.

Electrochemical Capacitance of Nanocomposite Films Formed by Coating Aligned Arrays of Carbon Nanotubes with Polypyrrole

Aligned MWNT–PPy composite films show exceptional charge storage capacities and improved response times. The superior performance of these composites, compared to pure PPy films, is demonstrated and discussed. The Figure shows an SEM image of the fractured film cross section, illustrating the thickness of the PPy coating as well as the channels available to the electrolyte.

Electrochemical Capacitance of a Nanoporous Composite of Carbon Nanotubes and Polypyrrole

This work reports the supercapacitive properties of electrochemically grown composite films of multiwalled carbon nanotubes (MWNT) and polypyrrole (PPy), a conducting polymer. Scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy revealed that the nanoporous three-dimensional arrangement of PPy-coated MWNTs in these films facilitated improved electron and ion transfer relative to pure PPy films. The low-frequency capacitance was measured for films of varying thickness, revealing specific capacitances per mass (Cmass) and geometric area (Carea) as high as 192 F g-1 and 1.0 F cm-2, respectively. Rates of charge and discharge about an order of magnitude faster than similarly prepared pure PPy films were also observed.

The Effect of Nanotube Loading and Dispersion on the Three-Dimensional Nanostructure of Carbon Nanotube-Conducting Polymer Composite Films

ABSTRACTNanoporous composite films of multi-walled carbon nanotubes (MWNTs) and either polypyrrole (PPy) or poly(3-methylthiophene) (P3MeT) were grown using an electrochemical polymerization technique in which the nanotubes and conducting polymer were deposited simultaneously. The concentration and dispersion of MWNTs in the polymerization electrolyte was found to have a significant effect on the thickness of polymer coated on each MWNT and hence the loading of MWNTs in the films produced. It has been shown that for an increasing concentration of MWNTs in the polymerization electrolyte, the thickness of polymer coated on each MWNT decreases. This relationship made it possible to minimize ionic diffusion distances within the nanoporous MWNT-PPy films produced, reducing their electrical and ionic resistance and increasing their capacitance relative to similarly prepared pure PPy films.

Doping and Electrochemical Capacitance of Carbon Nanotube-Polypyrrole Composite Films

ABSTRACTComposite films were electrochemically synthesised via the simultaneous deposition of multiwalled nanotubes and polypyrrole, a conducting polymer. Negatively charged functional groups attached to the surface of the acid treated nanotubes enables the tubes to act as a dopant for the PPy in these films. Scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy revealed that the nano-porous three-dimensional arrangement of PPy coated MWNTs in these films produced specific capacitances per mass and geometric area as high as 192 F g-1 and 1.0 F cm-2, respectively. This value of specific capacitance per geometric area exceeds that of both component materials and other carbon nanotube-conducting polymer composites. The composite films described in this report were also able to charge and discharge more than an order of magnitude faster than similarly prepared pure PPy films. The nano-porosity and small diffusion distances within the composite films, crucial to achieving the superior capacitive performance, were found to be dependent on the concentration of nanotubes and additional dopant anions in the polymerisation electrolyte, offering possibilities for tailoring of the composite structure.

Electrically Conductive Polymer Composite from Polypyrrole and Electrodeposited Poly(p-phenylene terephthalamide) Film

Electrically conductive composites from polypyrrole (PPy) and poly(p-phenylene terephthalamide) (PPTA) were formed by electropolymerization of pyrrole on the electrode covered with PPTA film prepared by electrolysis of PPTA polyanions dissolved in dimethylsulfoxide. For the PPTA film annealed above 250°C, the polymerization of pyrrole hardly took place. Based on DSC measurements, it was found that the remaining solvent of PPTA film was closely related to composite formation. The morphologies of the composites varied, depending on the supporting electrolytes of tetraethylammonium p-toluenesulfonate and lithium perchlorate. The conductivity of the composite was 5–50 S cm−1. The composite showed improved mechanical properties: tensile strength was 142 MPa and tensile modulus was 6.2 GPa for the PPy(TsO−)/PPTA composite, where TsO− denotes the p-toluenesulfonate ion. The temperature dependence of the dynamic viscoelasticity of the PPy(TsO−)/PPTA composite was well explained by Takayanagi’s two-phase model, which was also consistent with SEM observation. The conductivities of the composites doped with p-toluenesulfonate and perchlorate were both retained at all times up to 150°C, whereas that of the pure PPy film decreased to 80% the original value after annealing at 150°C, being independent of the dopants. PPTA film was dimensionally stable and heat-resistant, and these properties provided a stable conductive composite film.