Carbon materials, especially Vulcan XC-72 carbon black, are the most widely used catalyst support in low temperature fuel cells. Several disadvantages of these catalyst supports, however, limit the catalyst performance leading to reduced fuel cell performance and durability: low resistance to corrosion at high potentials, micropores leading to limited accessible surface, impermeability to gases and liquids, and no proton conductivity. Therefore, development of novel supports or modified carbon materials is essential to commercialization of low temperature fuel cell technology. Due to unique metallic/semiconductor characteristics along with excellent environmental stability, facile synthesis and high conductivity, polypyrrole (PPy), a member of the conjugated heterocyclic conducting polymers, has been considered the most promising alternative to carbon supports in fuel cells. Extensive research on PPy-containing catalysts has been reported in the last twenty years. This paper systematically and critically reviews the progress and main achievements of PPy use in both anode and cathode catalysts for low temperature fuel cells. Insight into the remaining challenges and future research directions is also discussed.

Use of polypyrrole in catalysts for low temperature fuel cells

Thermal, dielectric and microwave absorption properties of polyaniline–CoFe2O4 nanocomposites

Current challenges in the development of various polymer nanocomposites and in the study of their properties are considered. Results of studying hybrid structural (polymer–layered silicates, polymer–nanodiamonds) and functional (based on conducting or liquid-crystalline polymers) nanomaterials are presented. Methods of modification of nanoparticles and their dispersion in a polymer matrix, and the role of interactions between a polymer matrix and fillers, as well as of nanoparticle morphology realized in the course of processing, are discussed. The bibliography includes 453 references.

https://iopscience.iop.org/article/10.1070/RC2013v082n04ABEH004322/pdf

New approaches to the development of hybrid nanocomposites: from structural materials to high-tech applications

https://ir.nctu.edu.tw:443/bitstream/11536/8402/1/000259133300029.pdf

Synthesis and dielectric properties of polyaniline/titanium dioxide nanocomposites

Montmorillonite polyaniline nanocomposites: Preparation, characterization and investigation of mechanical properties

This paper describes the preparation and characterization of conducting polyaniline-montmorillonite (PANI-MMT) nanocomposites by the polymerization of anilinium ions within the interlayer space of MMT particles. A procedure for the successive introduction of PANI chains within the interlayer galleries of MMT is developed. The d-spacing, measured after heat treatment at various temperatures serves as a measure of the amount of polymer inserted in the clay intergalleries. The FTIR spectroscopy reveals the presence of host-guest interactions of a hydrogen-bonded nature. The DC conductivities were found to increase with the amount of PANI intercalated. Anilinium ions supported on kaolinite tended to dislodge from the surface upon repeated washings, as shown by the absence of polymer formation on such samples upon treatment with the oxidant. In MMT, however, polymerization is observed even with exhaustively washed samples, thus confirming that the successive polymerization processes occur within the interlayer...

Preparation, Characterization and Conducting Properties of Nanocomposites of Successively Intercalated Polyaniline (PANI) in Montmorillonite (MMT)

Cu(II)-exchanged montmorillonite [Cu(II)-MMT] takes up pyrrolium ions by ion exchange. Two pyrrolium ions are inserted for each Cu(II) ion expelled from its interlayers. These pyrrolium ions undergo spontaneous polymerization because of the remaining Cu(II) ions present within the intergalleries to form Cu(I)-polypyrrole-MMT nanocomposite. The polypyrrole (PPY) dispels any water already present within the intergalleries and the material becomes hydrophobic and reluctant to take up water. The inherent d-spacing due to anhydrous PPY present within the intergalleries is 16.0 A, which is a 6.4 A enhancement from the situation, which contains a bare inorganic ion. The material possesses unusually high mixed electrical conductivity. The conjugation length (and hence the electronic conductivity) decreases as the temperature is increased as confirmed by the Fourier transform infrared spectroscopy. However, the ionic component of the conductivity increases with temperature. The temperature dependence of conductivi...

Polypyrrole-montmorillonite nanocomposite: A composite fast ion conductor

Mixed-conducting polyaniline-Fuller's Earth nanocomposites prepared by stepwise intercalation

Investigation of the electrical properties of polymer–clay nanocomposites is important in the development of nanoelectronic devices. These nanocomposites may be prepared by intercalating suitable monomers within interlayer spaces of expanding layered clay materials, followed by in situ polymerization. We made use of this approach to prepare montmorillonite–polyaniline nanocomposites by ion-exchanging the intergallery cations for anilinium ions and subsequently polymerizing the anilinium ions by peroxydisulphate in the acidic medium to yield emeraldine salt form of polyaniline intercalated in montmorillonite (ES1-MMT). The emeraldine salt form of polyaniline contains one positive charge per three monomer units, and hence, polymerization of anilinium ions reduces the number of cations present within the interlayer. Charge compensation thus requires uptake of required amount of cations from the solution. Further, the emeraldine salt form of polyaniline can be neutralized by treating with excess base such as ammonia. Thus, the neutralization of emeraldine salt results in an uptake of ammonium ions for charge balance. We have, therefore, neutralized ES1-MMT using aqueous ammonium hydroxide, and the cations inserted into the interlayer were again exchanged for anilinium ions. The latter was polymerized in acidic medium to yield more polyaniline in its emeraldine salt form (ES2-MMT). By repeating this procedure we have also prepared ES3-MMT. X-ray diffraction (XRD) spectra recorded at 150 °C reveal the enhancement of d-spacing upon increased amounts of polymer formation, and the Fourier transform infrared (FTIR) analysis also supports this by showing enhanced absorption due to bands typical of emeraldine salt (for example, B–NH+ = Q, where B and Q stand for benzanoid and quinoid, respectively). Careful analyses of FTIR spectra reveal that the polymer is present within the interlayers, as well as adsorbed onto the external surfaces and is bound to clay layers through hydrogen bonding. In this publication, we report the electrical properties of such ES-MMT nanocomposites. Alternating current (AC) impedance analysis shows that the nanocomposites are highly conducting materials, and their bulk conductivity enhances in the order ES1-MMT < ES2-MMT < ES3-MMT. The materials are pure electronic conductors as revealed by the direct current polarization studies. Further, their conductivities decrease with increasing temperature as of pure electronic conductors. By treating kaolinite with anilinium ions in acidic medium followed by peroxydisulphate ions, emeraldine salt–kaolinite (ES-KAL) composites have also been prepared. Because kaolinite is a non-expanding clay, the ion exchange is not possible, and hence, the polymer cannot be incorporated into the interlayer. This is indeed shown in the XRD analysis. The polymer can only reside out of the kaolinite particles. FTIR spectra reveal the hydrogen bonding between the polymer and kaolinite outer surfaces. AC impedance spectra of ES-KAL do not show high bulk conductivity. Thus, the comparison of AC impedance spectra of ES-KAL with ES-MMT systems clearly indicates that the bulk conductivity of the latter systems is predominantly due to intercalated polyaniline.

AC impedance analysis of polyaniline–montmorillonite nanocomposites

A series of nanocomposites of polyaniline-montmorillonite have been prepared in which polyaniline is present within the interlayers as well as adsorbed onto the external surfaces of the clay particles (i.e., emeraldine salt-montmorillonite, ES-MMT series). The composite materials show uniform texture as revealed by scanning electron microscopy. The ES-MMT members show high electronic conductivities. Under the identical conditions of sample preparation, the d-spacing enhancement upon the polymer intercallation is the same regardless of whether the polymer is present only within intergalleries or both inside and outside the intergalleries. The FTIR studies reveal that the OH stretching in the Al-Mg-OH infrared band appearing at 840cm-1 disappears upon polymer loading. Since the OH in Al-Mg-OH moieties are directed outward from the hexagonal cavities, this effect may be attributed to the interaction between the clay particles and the polymer that is present adsorbed to clay surfaces. The polymer present with...

D. M. M. Krishantha

Papers

Preparation, Characterization and Conducting Properties of Nanocomposites of Successively Intercalated Polyaniline (PANI) in Montmorillonite (MMT)

Polypyrrole-montmorillonite nanocomposite: A composite fast ion conductor

Mixed-conducting polyaniline-Fuller's Earth nanocomposites prepared by stepwise intercalation

AC impedance analysis of polyaniline–montmorillonite nanocomposites

Electrochemical Impedance Spectroscopic and Other Studies of Polyaniline-Montmorillonite Intercalates: