Sundara Ramaprabhu

Cost-effective counter electrode (CE) with high electrocatalytic performance is very much essential for the wide application of dye-sensitized solar cells (DSSC). The 1D-2D carbon heterostructure (Pt/GR@CNT) with low platinum (Pt) loading has been synthesized by a facile in situ microwave-assisted polyol-reduction method. The excellent electrocatalytic activity as well as photovoltaic performance was achieved due to the combination of 2D graphene nanoribbons (GR) and 1D multi-walled carbon nanotubes (CNT) with high catalytically active Pt nanoparticles. Microwave-assisted longitudinal unzipping of few outer layers of CNTs along with co-reduction of Pt nanoparticles is an effective method to create electrochemically active defective edge sites, which have a crucial role in enhancing electrochemical performance. Synergistic effect of ultra-fine Pt nanoparticles, partially unzipped graphene nanoribbons and inner core tubes of CNTs modulates the power conversion efficiency of solar cell to 5.57% ± 0.03 as compared with 4.73% ± 0.13 of CNTs. Pt/GR@CNT CE even with low Pt loading of 14 μg cm−2 showcases equivalent performance with that of pure Pt counter electrode. [Figure not available: see fulltext.]

In the present wok, we have demonstrated the simultaneous removal of sodium and arsenic (pentavalent and trivalent) from aqueous solution using functionalized graphite nanoplatelets (f-GNP) based electrodes. In addition, these electrodes based water filter was used for multiple metals removal from sea water. Graphite nanoplatelets (GNP) were prepared by acid intercalation and thermal exfoliation. Functionalization of GNP was done by further acid treatment. Material was characterized by different characterization techniques. Performance of supercapacitor based water filter was analyzed for the removal of high concentration of arsenic (trivalent and pentavalent) and sodium as well as for desalination of sea water, using cyclic voltametry (CV) and inductive coupled plasma-optical emission spectroscopy (ICP-OES) techniques. Adsorption isotherms and kinetic characteristics were studied for the simultaneous removal of sodium and arsenic (both trivalent and pentavalent). Maximum adsorption capacities of 27, 29 and 32 mg/g for arsenate, arsenite and sodium were achieved in addition to good removal efficiency for sodium, magnesium, calcium and potassium from sea water. © 2010 Elsevier B.V.

Despite possessing 5-fold higher specific energy density compared to commercial lithium-ion batteries, the insulating nature of sulfur and its reductive derivatives along with the uncontrollable migration of polysulfides hinder the commercialization of lithium-sulfur technology. Herein a bilayer cathode consisting of nitrogen sulfur codoped porous carbon network and titanium carbide has been introduced and investigated methodically. The porous sulfur host promotes uninterrupted diffusion of electrolyte and ions whereas titanium carbide acts as polysulfide trapping material. The superiority of this bilayer cathode over the conventional interlayer approach has been highlighted in terms of the diffusivity of lithium ions and the overall ohmic resistance. Variation in interfacial charge transfer resistance during charging and discharging has been investigated using dynamic electrochemical impedance spectroscopy. Discharge capacity reaches as high as 1300 mA h g-1 at 0.1 C with a Coulombic efficiency of 99%. Theoretical studies reveal that the polar nature and improved interfacial charge transfer between the TiC and polysulfides result in excellent binding strength and faster redox kinetics during operation, respectively. This work provides an experimental as well as theoretical evidence of the bifunctional mechanism of TiC toward polysulfide confinement and conversion.

Materials play a key role especially in the field of energy storage and conversion. Design of efficient and cost-effective materials for energy applications is of prime research focus. This chapter presents the recent trends in the energy-related applications of various carbon nanotubes (CNT) and their hybrid nanostructures. Development of CNT-based electrocatalysts for proton exchange membrane fuel cells and CNT-based electrodes for supercapacitors and Li-ion batteries are discussed.

Herein, we report, the fabrication of a mechanically stable, flexible graphene based all-solid-state supercapacitor with ionic liquid incorporated polyacrylonitrile (PAN/[BMIM][TFSI]) electrolyte for electric vehicles (EVs). The PAN/[BMIM][TFSI] electrolyte shows high ionic conductivity (2.42 mS/cm at 28 °C) with high thermal stability. Solid-like layered phase of ionic liquid is observed on the surface of pores of PAN membrane along with liquid phase which made it possible to hold 400 wt% of mobile phase. This phase formation is facilitated by the ionic interaction of C. N moieties with the electrolyte ions. A supercapacitor device, comprised PAN/[BMIM][TFSI] electrolyte and graphene as electrode, is fabricated and the performance is demonstrated. Several parameters of the device, like, energy storage and discharge capacity, internal power dissipation, operating temperature, safe operation and mechanical stability, meet the requirements of future EVs. In addition, a good cyclic stability is observed even after 1000 cycles. © 2012 Elsevier Ltd.

The influence of Mm substitution (Mm = mischmetal) on structural, transport and magnetic properties of (Dy1-xMmx)Co2 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) alloys has been investigated by means of X-ray diffraction (XRD), temperature dependent electrical resistivity (ρ(T)), ac susceptibility (χ(T)) and thermopower (S(T)). XRD patterns show the formation of solid solutions crystallizing with cubic Laves (C15) type structure at room temperature. The pronounced discontinuities in the resistivity and thermopower at Curie temperature (TC) are explained based on the suppression of the spin-fluctuation contribution. The gradual decrease in TC and sharpness of discontinuities in ρ(T) and S(T) with increasing Mm substitution has been discussed. © 2008 Elsevier Ltd. All rights reserved.

The relative chemical potential of the dissolved hydrogen (Δμ0H) and the partial pair interaction free energies, gPH↔Z, and (gPH↔Z/Z)average respectively, in Pd based Pd1 - xZx-H and Pd1 - x - yZxZ′y-H systems are correlated to the stability of the dissolved hydrogen in the octahedral interstitial sites by classifying the Pd1 - xZx alloys based on the "effective valence, ns" of the substitutional metals. From the dependence of Δμ0H on the lattice constant of the alloy, (a0)alloy, and of gPH↔Z ((gPH↔Z/Z′)average) on the ionic diameter of the substituent metal, dZ, ((dZ/Z′)average) for systems Pd1 - xZx-H (Pd1 - x - yZxZ′y-H), the exceptional behavior of the binary "expanded" alloys Pd1 - xZx (Z = Nb, Ta and Pt), the binary "contracted" Pd1 - xZx alloys (Z = Ti and Li) and the ternary "contracted" alloys Pd0.903Er0.078Cu0.019 and Pd1 - 2xAgxNix towards hydrogen absorption is explained. © 1998 International Association for Hydrogen Energy.

Pressure-composition (P-C) hydrogen absorption isotherms have been obtained for MmNi3.5Al0.5Fe0.5Co0.5+0.5 wt% B and MmNi3.5Al0.5Fe0.5Co0.5 +25 wt% polyaniline (PANI) in the ranges 30-100 °C and 0.1-40 bar using a high pressure Seiverts' apparatus. The phase structure and microstructure morphologies of as-prepared and ball-milled materials have been analysed by XRD and SEM respectively. The effect of particle size, boron addition and PANI dispersion on the hydrogen absorption kinetics in MmNi3.5Al 0.5Fe0.5Co0.5 has been studied and discussed. The diffusion coefficient and activation energy of dissolved hydrogen in MmNi3.5Al0.5Fe0.5Co0.5, MmNi 3.5Al0.5Fe0.5Co0.5+0.5 wt% B and MmNi3.5Al0.5Fe0.5Co0.5+25 wt% PANI have been obtained from the studies of hydrogen absorption kinetics using the first order rate equation and the results have been discussed. © 2005 IOP Publishing Ltd.

Microbial Fuel Cells (MFC) are robust devices capable of taping biological energy, converting sugars into potential sources of energy. Persistent efforts are directed towards increasing power output. However, they have not been researched to the extent of making them competitive with chemical fuel cells. The power generated in a dual-chamber MFC using neutral red (NR) as the electron mediator has been previously shown to be 152.4 mW/m 2 at 412.5 mA/m 2 of current density. In the present work we show that Pt thin film coated carbon paper as electrodes increase the performance of a microbial fuel cell compared to conventionally employed electrodes. The results obtained using E. coli based microbial fuel cell with methylene blue and neutral red as the electron mediator, potassium ferricyanide in the cathode compartment were systematically studied and the results obtained with Pt thin film coated over carbon paper as electrodes were compared with that of graphite electrodes. Platinum coated carbon electrodes were found to be better over the previously used for microbial fuel cells and at the same time are cheaper than the preferred pure platinum electrodes. Copyright © 2008 American Scientific Publishers All rights reserved.

Carbon nanotubes have been prepared by the catalytic decomposition of acetylene over Ni/Cr hydrotalcite-type anionic clay catalyst. Ni/Cr hydrotalcite-type anionic clay precursors have been prepared by co-precipitation technique. The role of stability of Ni nanoparticles obtained in situ from the decomposition of the catalyst on the growth of MWNTs is discussed. The as-synthesized and purified carbon nanotubes are characterized by thermogravimetry, IR spectroscopy, X-ray diffraction, BET analysis, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy measurements. The hydrogen adsorption capacity of as-synthesized and purified multiwalled carbon nanotubes at 298 K has been obtained using a high-pressure hydrogen adsorption set-up and the results are discussed. © 2004 Elsevier B.V. All rights reserved.