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Jafri R.I.,Nano Functional Materials Technology Center | Rajalakshmi N.,Indian Institute of Technology Madras | Ramaprabhu S.,Nano Functional Materials Technology Center
Journal of Power Sources | Year: 2010

Multi-walled carbon nanocoils (MWNCs) are synthesized by chemical vapour deposition and nitrogen-doped MWNCs (N-MWNCs) are obtained by nitrogen plasma treatment. MWNCs and N-MWNCs are used as catalyst supports for platinum nanoparticles. Pt nanoparticles are dispersed over these support materials using the conventional chemical reduction technique and then used for the oxygen reduction reaction in proton-exchange membrane fuel cells. The morphology and structure of the MWNC-based powder samples are studied by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Full cells are constructed with Pt-loaded MWNC/N-MWNC and the results are discussed. A maximum power density of 550 and 490 mW cm -2 is obtained with Pt/N-MWNC and Pt/MWNC as the ORR catalyst, respectively. The improved performance of a fuel cell with a N-MWNC catalyst support can be attributed to the creation of pyrrolic nitrogen defects due to the nitrogen plasma treatment. These defects act as good anchoring sites for the deposition of Pt nanoparticles and to the increased electrical conductivity and improved carbon-catalyst binding. © 2010 Elsevier B.V. All rights reserved. Source

Jafri R.I.,Nano Functional Materials Technology Center | Ramaprabhu S.,Nano Functional Materials Technology Center
International Journal of Hydrogen Energy | Year: 2010

Multi walled carbon nanotubes (MWNTs) have been synthesized by chemical vapour deposition technique using AB3 alloy hydride catalyst. Platinum supported MWNTs (Pt/MWNTs) and platinum-tin supported MWNTs (Pt-Sn/MWNTs) electrocatalysts have been prepared by chemical reduction method. MWNTs and electrocatalysts have been characterized by powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), high resolution TEM (HRTEM) and Energy dispersive X-ray analysis (EDAX). The anode and cathode electrodes for DEFC have been fabricated using Pt-Sn/MWNTs and 1:1 Pt/MWNTs + Pt/C electrocatalyst respectively. Performances of Direct Ethanol Fuel Cell (DEFC) with these electrodes have been studied at different temperatures of the membrane electrode assembly at ambient fuel conditions and the results have been discussed. A maximum power density of 38.6 mW/cm2 at a current density of 130 mA/cm2 is obtained. A six cell planar Micro Direct Ethanol Fuel Cell (μ-DEFC) stack was also constructed using these electrocatalysts and etched printed circuit boards as anode and cathode current collectors. A maximum power density of 2 mW/cm2 was achieved when the μ-DEFC was operated in air breathing mode at room temperature. This enhancement of the performance may be attributed to dispersion and accessibility of MWNTs support and Pt-Sn in the electrocatalyst mixture for ethanol oxidation reaction. © 2009 Professor T. Nejat Veziroglu. Source

Kaniyoor A.,Nano Functional Materials Technology Center | Ramaprabhu S.,Nano Functional Materials Technology Center
Journal of Materials Chemistry | Year: 2012

Anchoring functional moieties on the surface of graphene is an important step in the processing of graphene for numerous applications. In this article, the effects of two different functionalization methods on graphene viz. the conventional method involving ultrasonication in acids and a novel polyelectrolyte based method are systematically investigated. While the conventional acid treatment method makes graphene highly hydrophilic, it also causes severe damage to the graphene sheets and leads to disordered restacking. In contrast, the soft functionalization method based on polyelectrolytes preserves the morphology to a significant extent. Moreover, the presence of charges on the surface of polyelectrolyte modified graphene causes mutual repulsion between the sheets, thereby assisting in the fabrication of optically transparent films. The presence of charges also affects the electrochemical behaviour towards tri-iodide reduction, which is investigated via electrochemical impedance spectroscopy. New equivalent circuits are proposed to interpret the observed response. © The Royal Society of Chemistry 2012. Source

Mishra A.K.,Nano Functional Materials Technology Center | Ramaprabhu S.,Nano Functional Materials Technology Center
Journal of Materials Chemistry | Year: 2012

The current scientific community is extensively involved in developing novel materials for energy and environmental applications. Capture of CO 2 to remove it from the atmosphere is one of the most important applications among them. In the present work, we have demonstrated for the first time, to the best of our knowledge, a polyaniline-graphene nanocomposite as a CO 2 capture candidate. Graphene was prepared by hydrogen induced thermal exfoliation of graphite oxide and was further coated with polyaniline using a chemical method. The nanocomposite was characterized by different techniques and the capture capacity was measured using a high pressure Sievert's apparatus. FTIR spectroscopy was used to confirm the possible CO 2 capture mechanism in the nanocomposite. CO 2 adsorption capacities at a pressure of 11 bar and different temperatures of 25, 50 and 100°C were experimentally found to be 75, 47 and 31 mmol g -1, respectively. This nanocomposite shows much higher CO 2 capture capacity compared to pure graphene and shows a high degree of recyclability. © 2012 The Royal Society of Chemistry. Source

Baby T.T.,Nano Functional Materials Technology Center | Ramaprabhu S.,Nano Functional Materials Technology Center
Talanta | Year: 2010

A new type of amperometric glucose biosensor based on silicon dioxide coated magnetic nanoparticle decorated multiwalled carbon nanotubes (Fe3O4@SiO2/MWNTs) on a glassy carbon electrode (GCE) has been developed. MWNTs have been synthesized by catalytic chemical vapour decomposition (CCVD) of acetylene over rare earth (RE) based AB3 alloy hydride catalyst. The as-grown MWNTs have been purified and further functionlized. Functionalized MWNTs have been decorated with magnetic Fe3O4 nanoparticles which have been uniformly coated with biocompatible SiO2 using a simple chemical reduction method. The characterization of magnetic nanoparticle modified MWNTs have been done by X-ray diffraction (XRD), Fourier transform infra red spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), energy dispersive X-ray analysis (EDX) and UV-vis spectroscopy. Amperometric biosensor has been fabricated by the deposition of glucose oxidase (GOD) over Nafion-solubilized Fe3O4@SiO2/MWNTs electrode. The resultant bioelectrode retains its biocatalytic activity and offers fast and sensitive glucose quantification. The performance of the biosensor has been studied using cyclic voltammetry and amperometry and the results have been discussed. The fabricated glucose biosensor exhibits a linear response from 1 μM to 30 mM with an excellent detection limit of 800 nM indicating the potential applications in food industries. © 2009 Elsevier B.V. All rights reserved. Source

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