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RISS 인기검색어
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- 저자 : Gnana kumar, Georgepeter (검색결과 30 건)
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Gnana kumar, G.,Joseph Kirubaharan, C.,Yoo, D.J.,Kim, A.R. Pergamon Press ; Elsevier Science Ltd 2016 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.41 No.30
<P>The ternary composite comprising reduced graphene oxide (rGO), poly(3,4-ethylenedioxythiophene) (PEDOT) and iron oxide (Fe3O4) nanorods is developed and its substantial contribution toward the green energy generation of air cathode microbial fuel cells (ACMFC) as an efficient oxygen reduction reaction (ORR) catalyst is evaluated by using the different electrochemical techniques under various regimes and conditions. The effectual distribution of needle like and cubic inverse spinel structured Fe3O4 nanorods over the PEDOT enveloped graphene sheets are elucidated from the electron micrographs and the growth and composite formation mechanisms of Fe3O4 and rGO/PEDOT/Fe3O4, respectively, are enunciated from the detailed structural characterizations. The extended surface area, high electrical conductivity, and large oxygen adsorption sites of rGO/PEDOT/Fe3O4 nanocomposite facilitate the excellent ORR kinetics, which yields the maximum ACMFC power density with the superior durability of more than 600 h. Thus the proposed strategy extends a new approach in bringing the advantages of active carbon, conductive polymer and nanomaterials in a single tool, which constructs the prepared ternary composite as a potential ORR contender to the commercially available catalysts. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>
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Gnana kumar, G.,Balanay, Mannix P.,Nirmala, R.,Kim, Dong Hee,Raj kumar, T.,Senthilkumar, N.,Kim, Ae Rhan,Yoo, Dong Jin American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.1
<P>The PVdF-HFP nanofiber membranes with different molecular weight were prepared by electrospinning technique and were investigated as solid state electrolyte membranes in quasi solid state dye sensitized solar cells (QS-DSSC). The homogeneously distributed and fully interconnected nano fibers were obtained for all of the prepared PVdF-HFP electrospun membranes and the average fiber diameters of fabricated membranes were dependent upon the molecular weight of polymer. The thermal stability of electrospun PVdF-HFP membrane was decreased with a decrement of molecular weight, specifying the high heat transfer area of small diameter nanofibers. The QS-DSSC fabricated with the lower molecular weight PVdF-HFP electrospun nanofiber membrane exhibited the power conversion efficiency of n = 5.38%, which is superior over the high molecular weight membranes and is comparable with the liquid electrolyte. Furthermore, the electrospun PVdF-HFP membrane exhibited long-term durability over the liquid electrolyte, owing to the higher adsorption and retention efficiencies of liquid electrolyte in its highly porous and interconnected nanofibers. Thus the proposed electrospun PVdF-H FP membrane effectively tackled the volatilization and leakage of liquid electrolyte and provided good photoconversion efficiency associated with an excellent stability, which constructs the prepared electrospun membranes as credible solid state candidates for the application of QS-DSSCs.</P>
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Gnana kumar, G.,Christy, Maria,Jang, Hosaeng,Nahm, Kee Suk Elsevier 2015 Journal of Power Sources Vol.288 No.-
<P><B>Abstract</B></P> <P>The graphene/cubic cobaltite oxide nanosheets (rGO/Co<SUB>3</SUB>O<SUB>4</SUB>) with a face centered cubic crystalline structure are synthesized and are exploited as effective cathode catalysts in high performance Lithium-air batteries. The morphological images enunciate that 220 nm average diameter of Co<SUB>3</SUB>O<SUB>4</SUB> nanosheets are effectively anchored over the graphene sheets and the diameter of individual nanoparticles that construct the cubic nanosheets is 5 nm. The growth and composite formation mechanisms of prepared nanostructures are identified from Raman and FT-IR spectroscopic techniques. rGO/Co<SUB>3</SUB>O<SUB>4</SUB> composite exhibits a lower voltage, high discharge capacity of 4150 mAh g<SUP>−1</SUP> and displays superior cyclability without any capacity losses, signifying the excellent rechargeability of the fabricated electrodes. The post mortem analysis of electrodes specify the existence of lithium peroxide (Li<SUB>2</SUB>O<SUB>2</SUB>), lithium oxide (Li<SUB>2</SUB>O) and lithium carbonate (Li<SUB>2</SUB>CO<SUB>3</SUB>) discharge products, revealing the involved electrochemical reaction of Lithium-air batteries. The excellent electrochemical properties of rGO/Co<SUB>3</SUB>O<SUB>4</SUB> composite is due to the combination of rapid electrokinetics of electron transport and high electrocatalytic activity toward oxygen reduction reaction given <I>via</I> the synergetic effects of rGO and cubic Co<SUB>3</SUB>O<SUB>4</SUB> nanosheets. These findings provide fundamental knowledge on understanding the influence of morphological and structural properties of graphene based nanostructures toward Lithium-air battery performances.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Reduction of GO and insitu generation of Co<SUB>3</SUB>O<SUB>4</SUB> nanosheets occurred concurrently. </LI> <LI> Synergetic interaction between Co<SUB>3</SUB>O<SUB>4</SUB> and rGO improved oxygen reduction rate. </LI> <LI> Co<SUB>3</SUB>O<SUB>4</SUB> centres involved reaction mechanism in Li-air battery is detailed. </LI> <LI> rGO/Co<SUB>3</SUB>O<SUB>4</SUB> exhibited a higher discharge capacity with an excellent cyclability. </LI> <LI> The lithium based discharge products in electrodes are systematically analyzed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Nanometer Sized Silver Particles Embedded Silica Particles—Spray Method
Gnana kumar, G,Karunagaran, B,Nahm, KeeSuk,Nimma Elizabeth, R Springer 2009 Nanoscale research letters Vol.4 No.5
<P>Spherical shaped, nanometer to micro meter sized silica particles were prepared in a homogeneous nature by spray technique. Silver nanoparticles were produced over the surface of the silica grains in a harmonized manner. The size of silver and silica particles was effectively controlled by the precursors and catalysts. The electrostatic repulsion among the silica spheres and the electro static attraction between silica spheres and silver particles make the synchronized structure of the synthesized particles and the morphological images are revealed by transmission electron microscope. The silver ions are reduced by sodium borohydride. Infra red spectroscopy and X-ray photoelectron spectroscopy analysis confirm the formation of silver–silica composite particles. Thermal stability of the prepared particles obtained from thermal analysis ensures its higher temperature applications. The resultant silver embedded silica particles can be easily suspended in diverse solvents and would be useful for variety of applications.</P>
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Gnana Kumar, G.,Kim, A.R.,Nahm, Kee Suk,Elizabeth, R. Pergamon Press ; Elsevier Science Ltd 2009 International journal of hydrogen energy Vol.34 No.24
Nafion membranes modified with silica and silica sulfuric acid are fabricated for the elevated temperature and lower humidity operation of proton-exchange membrane fuel cells. An incorporation of silica sulfuric acid promotes the amorphous phase which in turn influences the segmental motion of polymeric chains. By the endeavor of sulfonic acid moieties, ion channels are extended and facilitate the high ionic diffusion. With the hygroscopic effort, high water molecules retention is favored which provokes the self humidification of Nafion membrane. The electrochemical properties of the composite membranes are varied in terms of the permeation effect of different sized silica particles in to the viable channels of Nafion membrane. Though higher electrochemical properties are obtained for the Nafion-silica sulfuric acid composite membranes, a balance between the electrochemical and physical properties is also highly maintained as that of bare Nafion membrane. The inclusion of silica sulfuric acid provides more sulfonic acid functional groups for the conscription of electrochemical properties and ceramic property of the material strengthens the perfluorinated polymer back bone which collectively extends the fuel cell performance of composite Nafion membranes and influences its potential application.
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G. Gnana kumar,Ae Rhan Kim,남기석,유동진 한국물리학회 2011 Current Applied Physics Vol.11 No.3
Proton exchange membranes were fabricated by directly blending polyvinylidene fluoride―hexafluoro propylene with silica sulfuric acid for the application of direct methanol fuel cells. Morphological and structural characterizations of the prepared membranes were characterized by scanning electron microscopy and infrared spectroscopy, respectively. The performed thermal gravimetric analysis ensured high thermal stability of the prepared membranes. The ion transport and fuel permeation of the fabricated composite membranes were solely governed by the hydrophilic and hydrophobic regions of silica sulfuric acid and host polymer matrix, respectively. The fabricated composite membrane exhibited a maximum fuel cell power density of 43 mW/cm^2 through the high ionic conductivity and low fuel permeability parameters and can be considered as a good contender for direct methanol fuel cells.
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Raj kumar, T.,Jin Yoo, Dong,Kim, Ae Rhan,Gnana kumar, G. The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.17
<P>A simple one-pot green synthesis method is developed to prepare a platinum-palladium (Pt-Pd) bimetallic nanoparticle decorated reduced graphene oxide (rGO) nanocomposite using vermicast extract as a reducing and stabilization agent. Morphological analysis confirms the homogenous decoration of Pt-Pd nanoparticles over the rGO sheets. Structural studies verify that the fatty acids and amide groups of the vermicast extract play a foremost role in the reduction of graphene oxide (GO) and the metallic ions. Benefiting from bimetallic features and a precise carbon support, the dehydrogenation of ethylene glycol (EG) and CO tolerance toward EG oxidation is significantly enhanced for rGO/Pt-Pd. The enhanced electrocatalytic activity of rGO/Pt-Pd toward EG oxidation is quantified <I>via</I> its mass activity of 803.4 mA mg<SUP>−1</SUP>, which is higher than the prepared nanocatalysts and commercial Pt/C. Furthermore, rGO/Pt-Pd retains a high current density (85%) over 500 cycles from its initial value, revealing its robust tolerance against CO poisoning. Thus the adopted green approach affords a cost-efficient and biocompatible carbonaceous metal nanocomposite with desirable electrocatalytic activity and stability for EG electrooxidation, demonstrating its wide applicability in high performance energy conversion devices.</P>
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