Faculty Publications
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Item Nano ZnO-activated carbon composite electrodes for supercapacitors(2010) Muthu, M.S.; Bhat, D.K.; Aggarwal, A.; Prahladh Iyer, S.; Sravani, G.A symmetrical (p/p) supercapacitor has been fabricated by making use of nanostructured zinc oxide (ZnO)-activated carbon (AC) composite electrodes for the first time. The composites have been characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction analysis (XRD). Electrochemical properties of the prepared nanocomposite electrodes and the supercapacitor have been studied using cyclic voltammetry (CV) and AC impedance spectroscopy in 0.1 M Na2SO4 as electrolyte. The ZnO-AC nanocomposite electrode showed a specific capacitance of 160 F/g for 1:1 composition. The specific capacitance of the electrodes decreased with increase in zinc oxide content. Galvanostatic charge-discharge measurements have been done at various current densities, namely 2, 4, 6 and 7 mA/cm2. It has been found that the cells have excellent electrochemical reversibility and capacitive characteristics in 0.1 M Na2SO4 electrolyte. It has also been observed that the specific capacitance is constant up to 500 cycles at all current densities. © 2010 Elsevier B.V. All rights reserved.Item Effect of deposition method and the surfactant on high capacitance of electrochemically deposited MnO2 on stainless steel substrate(Elsevier B.V., 2013) SuhasiniManganese dioxide has been considered as a promising material for electrochemical supercapacitors. In order to obtain a high specific capacitance, MnO2 has been electrodeposited from an aqueous acidic solution of MnSO4 consisting of an ionic surfactant, namely, sodium lauryl sulphate (SLS) on stainless steel. The electrodeposited films of MnO2 in the presence of the surfactant possess greater porosity and hence greater surface area in relation to the films prepared in the absence of the surfactant. Cyclic voltammetry and galvanostatic charge-discharge cycling experiments reveal that specific capacitance is higher by about 22% due to the effect of SLS. © 2012 Published by Elsevier B.V.Item Magnetron sputtered MoO3/carbon nanotube composite electrodes for electrochemical supercapacitor(Elsevier B.V., 2013) Aravinda, L.S.; Nagaraja, K.K.; Bhat, K.; Badekai Ramachandra, B.Molybdenum oxide (MoO3) has been deposited on multiwalled carbon nanotubes (MWCNTs) using DC reactive magnetron sputtering of molybdenum for supercapacitor applications. The deposits of MoO3 have been developed under different intervals of time. The structure and surface morphology of the deposits have been characterized by means of X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM). X-ray diffraction peaks of the composite films reveal the formation of crystalline structure of MoO3. The electrochemical performance of the composite films was studied using cyclic voltammetry (CV), galvanostatic charge discharge and electrochemical impedance spectroscopy measurements. The composite film exhibits maximum specific capacitance of 70 F g-1 at a scan rate of 10 mV s-1 in 1 M Na2SO4 electrolyte. The nanocomposite electrode material shows specific capacitance which is almost four fold increase with respect to that of bare MWCNTs. The effect of coating duration on specific capacitance has been studied. The nanocomposite film is found to display good cycleability, even up to 1000 cycles. © 2013 Elsevier Inc. All rights reserved.Item ZnO/carbon nanotube nanocomposite for high energy density supercapacitors(2013) Aravinda, L.S.; Nagaraja, K.K.; Nagaraja, H.S.; Bhat, K.; Badekai Ramachandra, B.A facile, green and highly efficient method for the decoration of carbon nanotubes with ZnO was developed for the fabrication of binder-free composite electrode for supercapacitor applications. The nano composite was prepared by using reactive magnetron sputtering in Ar/O2 environment. This approach leads to more uniform coating with tuneable thickness, which alters the electrochemical performance of the nano composite electrodes. The structure and surface morphology of the composite film have been studied by means of X-ray diffraction (XRD) analysis, scanning electron microscopy and field emission scanning electron microscopy (FESEM). The XRD study reveals the formation of Wurtzite ZnO structure. The electrochemical performance of nano composite electrode was investigated using cyclic voltammetry, chronopotentiometry and electrochemical impedance measurements in non-aqueous electrolyte. The nano composite electrode shows significant increase in the specific capacitance up to 48 F g-1 with an energy density 13.1 Wh kg-1 in the potential range -2 V to 1 V. © 2013 Elsevier Ltd. All rights reserved.Item Binder free MoO3/multiwalled carbon nanotube thin film electrode for high energy density supercapacitors(2013) Aravinda, L.S.; Bhat, K.; Badekai Ramachandra, B.MoO3/multiwalled carbon nanotube (MWCNT) composites were prepared by Magnetron sputtering in Ar/O2 atmosphere. This will provide a greener alternative for the fabrication of binder free composite electrode for supercapacitor applications. MWCNT provides good support for the growth of MoO3 thin films. This integrated composite electrode exhibited specific capacitance of 93 F g-1 and a corresponding energy density of 7.28 Wh kg-1 in non-aqueous electrolyte, which is almost fourfold increase compared to the bare MWCNT. Also the electrode maintains high power density of 4930 W kg-1 at high current rates, suggesting a potential energy storage material for portable and consumer electronics. © 2013 Elsevier Ltd. All rights reserved.Item Solar exfoliated graphene and its application in supercapacitors and electrochemical H2O2 sensing(Elsevier Ltd, 2015) Moolayadukkam, M.; Huang, N.M.; Nagaraja, H.S.In the present study, graphene nanosheets are synthesized using sunlight irradiation focussed onto graphite oxide. The morphological characteristics of graphene are examined using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Raman spectroscopy and X-ray diffraction (XRD) are used for the structural characterization of the sample. The electrochemical performance is evaluated using cyclic voltammetry (CV), charge-discharge characteristics and impedance spectroscopy. A high specific capacitance value of 223 F g-1 is obtained using cyclic voltammetry. The electrochemical detection of H2O2, a common biological species using solar graphene is demonstrated. The impedance spectroscopy and CV are used to study the electrocatalytic activity of the material. High sensitivity of 64.79 ?A mM-1 cm-2 is reported. © 2015 Elsevier Ltd. All rights reserved.Item Fabrication and performance evaluation of hybrid supercapacitor electrodes based on carbon nanotubes and sputtered TiO2(Institute of Physics Publishing michael.roberts@iop.org, 2016) Aravinda, L.S.; Nagaraja, K.K.; Nagaraja, H.S.; Bhat, K.U.; Badekai Ramachandra, B.R.We report a simple and eco-friendly method for the fabrication of a titanium dioxide/functionalized multiwalled carbon nanotube (TiO2/FMWCNT) composite electrode for use in supercapacitors. The nanocomposite electrodes were formed by depositing titanium dioxide onto FMWCNTs using reactive magnetron sputtering, thus providing a green roue for the formation of the binder-free composite electrode. It is shown that the electrochemical performance of the fabricated electrodes can be altered by tuning the thickness of the titanium dioxide overlayer. The integrated nanocomposite electrode showed an improved specific capacitance of 90 Fg-1 in two-electrode configuration. © 2016 IOP Publishing Ltd.Item Activated carbon derived from non-metallic printed circuit board waste for supercapacitor application(Elsevier Ltd, 2016) Rajagopal, R.R.; Aravinda, L.S.; Rajarao, R.; Badekai Ramachandra, B.R.; Sahajwalla, V.Activated carbons (ACs) have been synthesized by using waste PCBs via physical activation subsequent to pyrolysis processes. The physical and chemical properties of the produced activated carbons were studied using nitrogen adsorption, FT-IR spectroscopy, RAMAN spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy techniques. Among the synthesized ACs, AC with the highest surface area of 700 m2 g-1 produced at 850 °C for a time interval of 5 h was subjected to electrochemical studies. Capacitance behaviour of the obtained AC sample has been evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GC-D) measurements and electrochemical impedance spectroscopy (EIS) technique. Specific capacitance (Cspec) values vary from 220, 185 and 156 F g-1 for corresponding scan rate of 30, 50 and 100 mV s-1 respectively. The well-developed surface area properties and good capacitance values associated with nitrogen functionalities indicates the AC developed is a good and suitable candidate for the supercapacitor fabrication. © 2016 Elsevier Ltd.Item Microwave assisted growth of stannous ferrite microcubes as electrodes for potentiometric nonenzymatic H2O2 sensor and supercapacitor applications(Elsevier Ltd, 2016) Bindu, K.; Sridharan, K.; Ajith, K.M.; Lim, H.N.; Nagaraja, H.S.Electrochemical sensors and supercapacitors are two noteworthy applications of electrochemistry. Herein, we report the synthesis of SnFe2O4 microcubes and Fe2O3 nanorods through a facile microwave assisted technique which are employed in fabricating the electrodes for nonenzymatic hydrogen peroxide (H2O2) sensor and supercapacitor applications. SnFe2O4 microcubes exhibited an enhanced specific capacitance of 172 Fg?1 at a scan rate of 5 mVs?1 in comparison to Fe2O3 nanorods (70 Fg?1). Furthermore, the H2O2 sensing performance of the fabricated SnFe2O4 electrodes through chronopotentiometry studies in 0.1 M PBS solution (at pH 7) with a wide linear range revealed a good sensitivity of 2.7 mV ?M?1 ?g?1 with a lowest detection limit of 41 nM at a signal-to-noise ratio of 3. These results indicate that SnFe2O4 microcubes are excellent materials for the cost effective design and development of efficient supercapacitors as well as nonenzymatic sensors. © 2016 Elsevier LtdItem Microwave assisted synthesis of rGO/ZnO composites for non-enzymatic glucose sensing and supercapacitor applications(Elsevier Ltd, 2017) Moolayadukkam, M.; Dhanush, S.; Rossignol, F.; Nagaraja, H.S.Zinc oxide (ZnO) and Graphene Oxide (GO) are known to show good electrochemical properties. In this paper, rGO/ZnO nanocomposites have been synthesised using a simple microwave assisted method. The nanocomposites are characterized using XRD, Raman, SEM and TEM. XRD reveals the wurtzite structure of ZnO and TEM shows the heterogeneous nucleation of ZnO nanocrystals anchored onto graphene sheets. The electrochemical properties of the rGO/ZnO nanocomposite enhanced significantly for applications in glucose sensors and supercapacitors. The non-enzymatic glucose sensor of this nanocomposite tested using cyclic voltammetry (CV) and chronoamperometry, exhibits high sensitivity (39.78 mA cm?2 mM?1) and a lower detection limit of 0.2 nM. The supercapacitor electrode of rGO/ZnO nanocomposite exhibits a significant increase in specific capacitance. © 2017 Elsevier Ltd and Techna Group S.r.l.