Solid-state thermal exfoliation of graphite nano-fibers to edge-nitrogenized graphene nanosheets for oxygen reduction reaction.

We demonstrate a simple, single-step and scalable synthesis of edge-nitrogenated graphene nanosheets (E-N-GNS) through thermal exfoliation of graphite platelet nanofibers (GPNF) in the presence of melamine. This material was characterized using different physical characterization techniques which divulges that, the edges are selectively functionalised with pyridinic and pyrrolic type nitrogens leading to the formation of E-N-GNS. Further, the electrocatalytic activity of E-N-GNS towards oxygen reduction reaction (ORR) in alkaline medium was studied using electrochemical techniques to reveal superior electrocatalytic activity of E-N-GNS towards ORR than that of GPNF, perhaps due to the incorporation of N at the edges. The cyclic voltammetry (CV), however, shows a 50 mV and 71 mV positive shift in the onset and peak potentials respectively, which in combination with the rotating ring disk electrode (RRDE) results suggest that ORR follows a direct four electron transfer path on E-N-GNS in comparison with a two electron path on GPNF modified electrodes. This E-N-GNS also shows superior stability for 5000 cycles along with a high methanol-tolerance and durability than that of benchmark ORR electrocatalyst Pt/C (20%) to suggest its potential applications in fuel cells and metal-air batteries.

Functionalisation of fabrics with conducting polymer for tuning capacitance and fabrication of supercapacitor.

Conducting polymer (polypyrrole (PPy) doped with anion) film has been coated on different textile substrates from a mild, room temperature wet in situ chemical polymerisation method exploiting pyrrole as a monomer and ferric chloride as an oxidant and compared their electrochemical capacitive behaviour by assembling as an unit cell supercapacitor. PPy composites were prepared with carbohydrate polymers like cotton, linen (Natural cellulosic fibre), modified cellulosic fibre-viscose rayon and synthetic polymer polyester fabrics to investigate the influence on electrochemical capacitance. The surface morphology and chemistry of these materials were analysed by SEM, FT-IR, and XRD. It reveals that the PPy has greater interaction with the cellulosic fabrics, but whereas surface deposition only has taken place with synthetic fibres. The capacitive behaviour of the PPy coated textiles were evaluated using cyclic voltammetry, impedance spectroscopy and charge-discharge analysis. A unit cell was fabricated to investigate the capacitive behaviour by assembling two symmetric textile electrodes separated by a solid polymer (PVA/1M H2SO4 gel) electrolyte membrane. The textile electrodes prepared with PPy-Cotton and PPy-Viscose exhibited the highest specific capacitance value of 268 F g(-1) and 244 F g(-1), respectively at a scan rate of 5 mV s(-1). The charge-discharge analysis also shows higher specific capacitance value for PPy-Viscose and PPy-Cotton. The focus of this research is to highlight a successful, simple and reproducible method for fabrication of the textile based supercapacitor and the chemistry of surface interaction of PPy molecule with natural and synthetic fabrics.

One pot synthesis of polypyrrole silver nanocomposite on cotton fabrics for multifunctional property.

Polymer-silver nanocomposites modified cotton fabrics were prepared by in situ chemical oxidative polymerization using pyrrole and silver nitrate. In a redox reaction between pyrrole and silver nitrate, silver ions oxidize the pyrrole monomer and get reduced. This reduced silver as nanoparticles deposited on/into the polypyrrole/cotton matrix layer and the interaction between silver and polypyrrole was by adsorption or electrostatic interaction. The structure and composite formation on cotton fiber was investigated using SEM, FT-IR, XPS and XRD. The results showed that a strong interaction existing between silver nanoparticles with polypyrrole/cotton matrix. FT-IR studies clearly indicated that the interaction between polypyrrole (-N-H) and cellulose (>C-OH) was by hydrogen bonding. It is observed that the conductivity of the composite coated fabrics has been increased by the incorporation of silver nanoparticles. In the synthesized composites, silver content plays an important role in the conductivity and antimicrobial activity rate of the fabrics against gram positive Staphylococcus aureus and gram negative Escherichia coli bacteria.