Nafion membranes modified with silica sulfuric acid for the elevated temperature and lower humidity operation of PEMFC

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.

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>

Cobaltite oxide nanosheets anchored graphene nanocomposite as an efficient oxygen reduction reaction (ORR) catalyst for the application of lithium-air batteries

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>

Ultrasound assisted formation of Mn₂SnO₄ nanocube as electrodes for high performance symmetrical hybrid supercapacitors

Gnana Sundara Raj, Balasubramaniam,Kim, Hak-Yong,Kim, Byoung-Suhk Elsevier 2018 ELECTROCHIMICA ACTA Vol.278 No.-

<P><B>Abstract</B></P> <P>In this work, we have synthesized Mn<SUB>2</SUB>SnO<SUB>4</SUB> material with nanocube morphology from MnSn(OH)<SUB>6</SUB> intermediate via a simple one-pot sonochemical synthesis. The structural and morphological studies of the material were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The Mn<SUB>2</SUB>SnO<SUB>4</SUB> nanocubes were used as the active electrode material for supercapacitor applications. It delivered a maximum specific capacitance of 298 F g<SUP>-1</SUP> at a current density of 1 mA cm<SUP>−2</SUP>. The Mn<SUB>2</SUB>SnO<SUB>4</SUB> nanocubes showed excellent cycle stability with capacitance retention of 89% over 5000 cycles and desirable rate capability retain 223 F g<SUP>-1</SUP> at a current density of 15 mA cm<SUP>−2</SUP> in a three electrode system. Further, these materials were applied to the symmetric supercapacitor device, and it exhibited high specific capacitance (144 F g<SUP>-1</SUP> at 3 mA cm<SUP>−2</SUP>), good cycle stability (75% capacitance retention after 1000 cycles), high energy density (30.4 Wh kg<SUP>−1</SUP>) and power density (7.9 kW kg<SUP>-1</SUP> at 26.4 Wh kg<SUP>−1</SUP>) in a potential range of 2 V in 1 M Na<SUB>2</SUB>SO<SUB>4</SUB> aqueous electrolyte. These results suggest that Mn<SUB>2</SUB>SnO<SUB>4</SUB> nanocubes show suitable electrode material for high-performance supercapacitor applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mn<SUB>2</SUB>SnO<SUB>4</SUB> nanocubes was synthesized by simple one-pot sonochemical synthesis. </LI> <LI> Mn<SUB>2</SUB>SnO<SUB>4</SUB> nanocubes showed an excellent specific capacitance with good long-term stability. </LI> <LI> The fabricated symmetric supercapacitor showed the maximum energy density of 30.4 Wh kg<SUP>−1</SUP> and power density 7.9 kW kg<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The Photovoltaic Performances of PVdF-HFP Electrospun Membranes Employed Quasi-Solid-State Dye Sensitized Solar Cells

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>

Power System Planning and Cost Forecasting Using Hybrid Particle Swarm-Harris Hawks Optimizations

Gnana Malar A. Jasmine,Sellamuthu Suseela,Ganga M.,Mahendran N.,Hoseinzadeh Siamak,Ahilan A. 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.2

Hybrid renewable-based power production has emerged as a crucial development in the electrical power system because to its ability to supply consumers with cost-efective and carbon-free electricity. Incorporating several renewable energy sources and storage systems with a grid-connected system necessitates extra design requirements, which raising the renewable system’s overall cost. Therefore, optimizing the size of the components is essential to minimizing the cost of the system and limiting its negative impacts. This paper presents a hybrid of Particle Swarm Optimization (PSO) and Harris Hawks Optimization (HHO) known as PSHHO technique-based economic analysis of smart grid (SG) Hybrid Renewable Energy Systems (HRES). Here, the hybrid PSHHO approach is presented to tackle the problem of HRES cost analysis. The major purpose of this study is to minimize the system cost and increase overall system efciency. Finally, the proposed approach is tested in the MATLAB tool, and the performance of the proposed method is compared with other existing methods such as HHO, PSO, and WOA. The result demonstrates the proposed system can meet the load demand with low Cost of Energy (COE) (21.5 Rs/kWh) than existing methods.

Graphene/poly(3,4-ethylenedioxythiophene)/Fe₃O₄ nanocomposite - An efficient oxygen reduction catalyst for the continuous electricity production from wastewater treatment microbial fuel cells

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>

High proton conductivity and low fuel crossover of polyvinylidene fluorideehexafluoro propylene―silica sulfuric acid composite membranes for direct methanol fuel cells

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.

Experimental and numerical study of an innovative 4-channels cold-formed steel built-up column under axial compression

Beulah Gnana Ananthi G,Krishanu Roy,James B. P. Lim 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.4

This paper reports on experiments addressing the buckling and collapse behavior of an innovative built-up coldformed steel (CFS) columns. The built-up column consists of four individual CFS lipped channels, two of them placed back-toback at the web using two self-drilling screw fasteners at specified spacing along the column length, while the other two channels were connected flange-to-flange using one self-drilling screw fastener at specified spacing along the column length. In total, 12 experimental tests are reported, covering a wide range of column lengths from stub to slender columns. The initial geometric imperfections and material properties were determined for all test specimens. The effect of screw spacing, load-versus axial shortening behaviour and buckling modes for different lengths and screw spacing were investigated. Nonlinear finite element (FE) models were also developed, which included material nonlinearities and initial geometric imperfections. The FE models were validated against the experimental results, both in terms of axial capacity and failure modes of built-up CFS columns. Furthermore, using the validated FE models, a parametric study was conducted which comprises 324 models to investigate the effect of screw fastener spacing, thicknesses and wide range of lengths on axial capacity of back-to-back and flange-to-flange built-up CFS channel sections. Using both the experimental and FE results, it is shown that design in accordance with the American Iron and Steel Institute (AISI) and Australia/New Zealand (AS/NZS) standards is slightly conservative by 6% on average, while determining the axial capacity of back-to-back and flange-to-flange built-up CFS channel sections.

New criteria to fix number of hidden neurons in multilayer perceptron networks for wind speed prediction

K. Gnana Sheela,S.N. Deepa 한국풍공학회 2014 Wind and Structures, An International Journal (WAS Vol.18 No.6

This paper proposes new criteria to fix hidden neuron in Multilayer Perceptron Networks for wind speed prediction in renewable energy systems. To fix hidden neurons, 101 various criteria are examined based on the estimated mean squared error. The results show that proposed approach performs better in terms of testing mean squared errors. The convergence analysis is performed for the various proposed criteria. Mean squared error is used as an indicator for fixing neuron in hidden layer. The proposed criteria find solution to fix hidden neuron in neural networks. This approach is effective, accurate with minimal error than other approaches. The significance of increasing the number of hidden neurons in multilayer perceptron network is also analyzed using these criteria. To verify the effectiveness of the proposed method, simulations were conducted on real time wind data. Simulations infer that with minimum mean squared error the proposed approach can be used for wind speed prediction in renewable energy systems.