Faculty Publications
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Item Organic-inorganic hybrid mixed-valent bisphosphonate-polyoxovanadates composites with activated carbon for energy storage applications(Nova Science Publishers, Inc., 2024) Madhusree, J.E.; Banerjee, A.; Mal, S.S.In this book, we discuss the investigation of two different bisphosphonate-functionalized polyoxovanadate compounds for use in electrochemical energy storage applications. The compounds are (NH4)4[H6(VIVO2)(VV2O5)2O3P-C(O)(CH2-2-C5NH4)-PO32].9H2O (m), and (NH4)4[H6(VIVO2)(VV2O5)2O3P-C(O)(CH2-3-C5NH4)-PO32]. 8H2O (n). They have a mixed-valent oxovanadate polyanionic assembly that has two different pyridyl functional groups present on the organic bisphosphonate ligand. Several techniques have been used to characterize composites made from these compounds with activated carbon, including Fourier transform infrared spectroscopy, P-XRD, FESEM, EDX, and surface adsorption-desorption tests. The electrochemical performance of acidic electrolytic solutions containing 0.1 M H2SO4, AC-m, and AC-n electrode materials was investigated. Although the compounds are isotypic mixed-valence polyoxovanadate structures, their electrical behavior varies based on the position of the pyridyl group. AC-n was reported to have the most prominent specific capacitance of 313 F g-1 at a current density of 1 A g-1 in a voltage window of 0-1 V, with exceptional energy and power densities of 43.56 Wh kg-1 and 1999.72 W kg-1, respectively. At the same time, AC-m exhibited a specific capacitance of 212 F g-1 and a specific energy of 29.45 Wh kg-1. By lighting up different LED lights with only 42 mg of carbon clothcoated sample, the composite AC-n electrode displayed exceptional specific power. A further benefit of AC-n nanohybrids is their ability to retain electrochemical performance over time, which suggests long-term stability. © 2024 Nova Science Publishers, Inc. All rights reserved.Item Flexible binder free functionalized carbon nanotube electrodes for ultracapacitor(SPIE spie@spie.org, 2014) Badekai Ramachandra, B.R.; Aravinda, L.S.; Bhat, K.U.The Flexible supercapacitor electrode material was prepared by simple spray coating technique. This will provide a greener alternative for the fabrication of binder free composite electrode for supercapacitor applications. A symmetric double layer super capacitor stack was fabricated by using flexible electrodes. The investigation of the capacitance property of the fabricated super capacitor stack was investigated using cyclic voltammetry, chronopotentiometry and electrical impedance spectroscopy studies. The flexible electrode material shows a specific capacitance of 50 Fg-1 with good cyclibility. © 2014 SPIE.Item Sustainable Off-Grid Electricity Generation System for Low Power Lighting in Remote Locations(Institute of Electrical and Electronics Engineers Inc., 2020) Shenoy, B.B.; Mitra, J.; Shripathi Acharya, U.; Laxminidhi, T.This paper proposes an environmental friendly and sustainable approach to generate electricity for small lighting applications in rural and remote locations. In the proposed system, human muscle energy, abundantly available in rural and remote locations, has been converted into electrical energy to be stored in an alternative energy storage device, e.g. a supercapacitor. The usual bicycle with a minor modification is plugged to a charging platform. The charging platform has a power processing circuit and a Permanent Magnet Direct Current generator. The system has the ability to power up a 1 W white LED lamp for a duration of approximately 60 minutes, when the bicycle is pedaled for 4 minutes. The proposed system is not only eco-friendly, but also effectively caters to the challenges posed by seasonal variations and locational disadvantages and is targeted specifically for locations which are not having access to the power grid. © 2020 IEEE.Item Analysis of Leakage Current Mechanism in Supercapacitor with Experimental Approach(Institute of Electrical and Electronics Engineers Inc., 2022) Bairwa, B.; Pareek, K.; Sarvagya, M.; Yaragatti, U.R.In this paper, we evaluated the leakage current of super capacitor during self-discharge. A three branch electrical equivalent circuit model (ECM) is constructed to estimate voltage response and leakage current of commercially available 2.7 V 350F (BCAP350) double-layer capacitor (DLC). Experimental work carried out with two constant current charging segments 0.25 ampere, and 0.5 amperes. Simulated data shows good agreement with experimental results obtained at electro-chemical workstation CH760e with RMSE and MAE error up to 0.0633, 0.05715, and 0.0759, 0.04173 for 0.25 ampere and 0.5 amperes charging current, respectively. The results confirm that the ECM model is capable to simulate the complex terminal behavior of the super capacitor and provides the means to study its application as an energy storage device. © 2022 IEEE.Item LiClO4 doped cellulose acetate as biodegradable polymer electrolyte for supercapacitors(2008) Muthu, M.S.; Bhat, D.K.The possibility of producing a biodegradable polymer electrolyte based on cellulose acetate (CA) with varied concentration of LiClO4 for use in supercapacitors has been investigated. The successful doping of the CA films has been analyzed by FTIR and DSC measurements of the LiClO4 doped CA films. The ionic conductivity of the films increased with increase in salt content and the maximum ionic conductivity obtained for the solid polymer electrolyte at room temperature was 4.9 × 10-3 ?-1for CA with 16% LiClO4. The biodegradation of the solid polymer electrolyte films have been tested by soil burial, degradation in activated sludge, and degradation in buffer medium methods. The extent of biodegradation in the films has been measured by AC Impedance spectroscopy and weight loss calculations. The study indicated sufficient biodegradability of the materials. A p/p poly-pyrrole supercapacitor has been fabricated and its electro-chemical characteristics and performance have been studied. The supercapacitor showed a fairly good specific capacitance of 90 F g-1 and a time constant of 1 s. © 2008 Wiley Periodicals, Inc.Item Polyvinyl alcohol-polystyrene sulphonic acid blend electrolyte for supercapacitor application(2009) Muthu, M.S.; Bhat, D.K.A new polymer blend electrolyte based on poly vinyl alcohol and poly styrene sulphonic acid has been studied as an electrolyte for supercapcitors. A carbon-carbon supercapacitor has been fabricated using this electrolyte and its electrochemical characteristics and performance have been studied. The conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. The real and imaginary parts of the electrical modulus of samples show a long tail feature, which can be attributed to high capacitance of the material. The super capacitor showed a fairly good specific capacitance of 40 F g- 1 and a time constant of 5 s. © 2008 Elsevier B.V. All rights reserved.Item LiClO4-doped plasticized chitosan as biodegradable polymer gel electrolyte for supercapacitors(2009) Muthu, M.S.; Bhat, D.K.Studies on redox supercapacitors using electronically conducting polymers are of great importance for hybrid power sources and pulse power applications. In this study, electrochemical properties of a chitosan-based biodegradable polymer gel electrolyte (PGE) and a p/p polypyrrole supercapacitor fabricated using this electrolyte have been investigated. The variation of conductivity and dielectric properties of the electrolyte film with temperature has also been measured. The PGE film chosen for the study exhibited a specific conductivity of 5.5 × 10-3 S cm~. The electric modulus of the electrolyte film exhibits a long tail feature indicative of good capacitance. The fabricated supercapacitor showed a fairly good specific capacitance of 120 F g-1 and a time constant of 1 s. © 2009 Wiley Periodicals, Inc.Item Microwave synthesized nanostructured TiO 2 -activated carbon composite electrodes for supercapacitor(Elsevier B.V., 2012) Muthu, M.; Bhat, D.K.Electrochemical properties of a supercapacitor based on nanocomposite electrodes of activated carbon with TiO 2 nano particles synthesized by a microwave method have been determined. The TiO 2 /activated carbon nanocomposite electrode with a composition of 1:3 showed a specific capacitance 92 Fg -1 . The specific capacitance of the electrode decreased with increase in titanium dioxide content. The p/p symmetrical supercapacitor fabricated with TiO 2 /activated carbon composite electrodes showed a specific capacitance of 122 Fg -1 . The electrochemical behavior of the neat TiO 2 nanoparticles has also been studied for comparison purpose. The galvanostatic charge-discharge test of the fabricated supercapacitor showed that the device has good coulombic efficiency and cycle life. The specific capacitance of the supercapacitor was stable up to 5000 cycles at current densities of 2, 4, 6 and 7 mA cm -2 . © 2012 Elsevier B.V.Item LiClO4-doped plasticized chitosan and poly(ethylene glycol) blend as biodegradable polymer electrolyte for supercapacitors(Institute for Ionics, 2013) Sudhakar, Y.N.; Muthu, M.; Bhat, D.K.Biodegradable polymer electrolyte comprising the blend of chitosan (CS) and poly(ethylene glycol) (PEG) plasticized with ethylene carbonate and propylene carbonate, as host polymer, and lithium perchlorate (LiClO4), as a dopant, was prepared by solution casting technique. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. The variation of conductivity and dielectric properties has been investigated as a function of polymer blend ratio, plasticizer content and LiClO4 concentration at temperature range of 298-343 K. The DSC thermograms show two broad peaks for CS/PEG blend and increased with increase in the LiClO4 content. The maximum conductivity has been found to be 1. 1 × 10-4 S cm-1 at room temperature for 70:30 (CS/PEG) concentration. The electric modulus of the electrolyte film exhibits a long tail feature indicative of good capacitance. The activation energy of all samples was calculated using the Arrhenius plot, and it has been found to be 0. 12 to 0. 38 eV. A carbon-carbon supercapacitor has been fabricated using this electrolyte, and its electrochemical characteristics and performance have been studied. The supercapacitor showed a fairly good specific capacitance of 47 F g-1. © 2012 Springer-Verlag.Item Tubular array, dielectric, conductivity and electrochemical properties of biodegradable gel polymer electrolyte(Elsevier Ltd, 2014) Sudhakar, Y.N.; Muthu, M.; Bhat, D.K.A supercapacitor based on a biodegradable gel polymer electrolyte (GPE) has been fabricated using guar gum (GG) as the polymer matrix, LiClO4 as the doping salt and glycerol as the plasticizer. The scanning electron microscopy (SEM) images of the gel polymer showed an unusual tubular array type surface morphology. FTIR, DSC and TGA results of the GPE indicated good interaction between the components used. Highest ionic conductivity and lowest activation energy values were 2.2 × 10-3 S cm-1 and 0.18 eV, respectively. Dielectric studies revealed ionic behavior and good capacitance with varying frequency of the GPE system. The fabricated supercapacitor showed a maximum specific capacitance value of 186 F g -1 using cyclic voltammetry. Variation of temperature from 273 K to 293 K did not significantly influence the capacitance values obtained from AC impedance studies. Galvanostatic charge-discharge study of supercapacitor indicated that the device has good stability, high energy density and power density. © 2013 Elsevier Ltd. All rights reserved.