Faculty Publications
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Publications by NITK Faculty
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Item N and p doped poly(3,4-ethylenedioxythiophene) electrode materials for symmetric redox supercapacitors(2007) Bhat, D.K.; Muthu, M.S.A symmetric redox supercapacitor has been fabricated based on n and p doped Poly(3,4-ethylenedioxythiophene)(PEDOT) coated on stainless steel (SS) electrodes. The characterization and performance of the supercapacitor has been studied by FTIR, Cyclic Voltammetry and AC Impedance spectroscopy. The supercapacitor showed a maximum specific capacitance of 121 F g-1 at a scan rate of 10 mV s-1. The time constant calculated for the supercapacitor through the active-reactive power behavior measurement was 12 milliseconds indicating the suitability of the system for efficient use at low frequency range. © 2007 Springer Science+Business Media, LLC.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 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 Effect of acid dopants in biodegradable gel polymer electrolyte and the performance in an electrochemical double layer capacitor(Institute of Physics Publishing custserv@iop.org, 2015) Sudhakar, Y.N.; Muthu, M.; Bhat, D.K.Proton-conducting biodegradable gellan gum gel polymer electrolytes (GPEs) have been prepared using three different dopants, namely ortho-phosphoric (o-H3PO4), sulfuric (H2SO4) and hydrochloric acids (HCl). The GPEs were cross-linked using borax. The polymeric gels were characterized by spectroscopic, thermal, ionic conductivities and dielectric measurements. Proton conductivity was in the range of 5.1 × 10-3 to 3.7 × 10-4 s cm-1 and activation energies were between 0.14 meV and 0.19 meV, at different temperatures. Among the doped acids, the H3PO4 doped GPE exhibited thermal stability at varying temperature. Electrochemical double layer capacitors (EDLCs) were fabricated using activated carbon as electrode material and GPEs. The EDLCs were tested using cyclic voltammetry, ac impedance spectroscopic and galvanostatic charge-discharge techniques. The maximum specific capacitance value was 146 F g-1 at a scan rate of 2 mV s-1. Quite stable values were obtained at a constant current density up to 1000 cycles. © 2015 The Royal Swedish Academy of Sciences.Item Facile solvothermal synthesis and high supercapacitor performance of NiCo2O4 nanorods(Elsevier Ltd, 2019) Sethi, M.; Bhat, D.K.NiCo2O4 nanorod arrays were synthesized employing a facile low-temperature solvothermal approach, followed by post-calcination treatment. The structural, morphological and elemental characterizations were done by diffraction, microscopic and spectroscopic techniques. The prepared sample was studied as an active electrode material for supercapacitor application in 2 M KOH aqueous electrolyte. The cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectral (EIS) studies were carried out to know the electrochemical activity of the prepared material. From the CV study, a high capacitance value of 440 F g?1 was obtained at a scan rate of 5 mV s?1 in a 3-electrode method. Apart from high capacitance value, the prepared electrode depicted 94% initial capacitance retention value after 2000 charge-discharge cycles at a current density of 8 A g?1. The fabricated symmetrical supercapacitor depicted a high energy density of 12.6 Wh kg?1 and a high power density of 4003 W kg?1. This was attributed to the better electrical conductivity of NiCo2O4 nanorods. © 2018 Elsevier B.V.Item Porous graphene-NiCo2O4 nanorod hybrid composite as a high performance supercapacitor electrode material(Royal Society of Chemistry, 2020) Sethi, M.; Shenoy, U.S.; Bhat, D.K.The template free low temperature solvothermal synthesis of high capacitive porous graphene-NiCo2O4 nanorod composites has been carried out. Solvothermal synthesis followed by calcination in air led to the development of a highly porous hybrid nanocomposite, which acts as a buffering channel for fast ion diffusion and provides robust mechanical strength. Advantages of using porous graphene to enhance the capacitance of the material were studied theoretically using First principles calculations. High capacitance values of 1533 F g-1 at a scan rate of 5 mV s-1 and 1684 F g-1 at a current density of 1 A g-1 are obtained from cyclic voltammetry data and galvanostatic charge discharge data, respectively. The electrode material possesses good cyclic stability with the retention of 94% of its initial capacitance even after 10000 charge-discharge cycles at a current density of 8 A g-1 in 2 M KOH electrolyte. The fabricated supercapacitor exhibited a high energy density of 45.3 W h kg-1 and a high power density of 17843.5 W kg-1 due to the synergistic effect of the composite components. The enhanced electrochemical function of the composite makes it a potential candidate for supercapacitor application and future studies. This journal is © 2020 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item Simple solvothermal synthesis of porous graphene-NiO nanocomposites with high cyclic stability for supercapacitor application(Elsevier Ltd, 2021) Sethi, M.; Shenoy, U.S.; Bhat, D.K.Over the years supercapacitors have established themselves as energy storage devices as well as a subject to reckon with. Thus, not surprisingly tremendous effort has been put in the field of supercapacitor research. However, a device with all desirable characteristics has not yet been realized and hence deserves to be paid utmost heed. Herein, we report a facile synthesis of porous graphene-NiO (PGNO) nanocomposites via a unique mixed solvent system through a solvothermal approach. The microscopic characterization of porous graphene (PG) reveals the presence of pores in the graphene sheets, NiO (NO) shows flake like structure and PGNO composite displays the anchoring of NO nanoflakes on the PG sheets. A series of electrode materials were prepared by varying the percentage composition of PG and the materials were named as 5–30 PGNO, respectively. The electrochemical study represented a good capacitance value of 511.0 F g?1 at a scan rate of 5 mV s?1 for the 10 PGNO composite in a 3-electrode method and 80% retention of initial capacitance after 10,000 cycles at a current density of 8 A g?1. The fabricated symmetrical hybrid supercapacitor by using the 10 PGNO electrodes also depicted a good capacitance value of 86.0 F g?1 at a scan rate of 5 mV s?1. The fabricated device retained 84% of initial capacitance at the end of 10,000 cycles at a current density of 8 A g?1, demonstrating the good electrochemical strength and rate capability of the material. The percentage of double layer capacitance and pseudocapacitance contributions to the overall specific capacitance of the PGNO supercapacitor has also been estimated. Overall, the results exhibited by the composite material warrants its beneficial utility in energy storage devices. © 2020 Elsevier B.V.Item Hassle-free solvothermal synthesis of NiO nanoflakes for supercapacitor application(Elsevier B.V., 2021) Sethi, M.; Shenoy, U.S.; Bhat, D.K.A mixed solvent solvothermal approach was employed for the synthesis of NiO (NO) nanostructures under a low temperature route. The nanoflakes when studied for its electrochemical performance in a 3-electrode method in aqueous 2 M KOH revealed a high capacitance value of 305.0 F g?1 at a scan rate of 5 mV s?1 apart from good rate capability, cyclic stability and coulombic efficiency. The fabricated symmetrical supercapacitor device also showed good electrochemical performance of pseudocapacitive nature with a high power density of 8000.0 W kg?1. The extent of surface sites taking part in the electrochemical processes reveals the enhanced performance is due to the high surface area of NO with a mesoporous structure. The enhanced conductivity of the nanoflakes also provided an unhindered path way for the ionic transport. The promising results reveal that the synthetic technique employed could be extended to other oxides as well. © 2021 Elsevier B.V.