Faculty Publications
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Item Effect of current density and electrochemical cycling on physical properties of silicon nanowires as anode for lithium ion battery(Elsevier Inc. usjcs@elsevier.com, 2017) Ramesh, R.; H.S., N.Herein, we successfully fabricated vertically aligned silicon nanowires (Si NWs) via an electrochemical etching of n-type (100) silicon at different high current densities. The morphology of the prepared Si NWs was studied using SEM, FFT analysis and WSxM software. From FTIR spectroscopy analysis, the silicon dangling bonds of the as-prepared Si NWs layer have large amount of hydrogen to form weak Si[sbnd]H bonds. The blue shift was observed in Photoluminescence due to decrease in the size of silicon crystallites, the crystallite size in the Si NWs varied from 5.9 nm to 4.8 nm depending on the current density. The contact angle varied from 74.7° to 149.1°. From the wettability studies, the surface nature of the Si NWs was converted from hydrophilic to hydrophobic when the current density increased. The obtained Si NWs were used as an anode in lithium ion cell. The charge capacity of the anode is ~ 3452.47 mAh g? 1 at the first cycle with the coulombic efficiency over 85.8%, and faded to 1134.34 mAh g? 1 with coulombic efficiency over 81.6% after the 12th cycle at a current rate of 1C. Scanning electron microscopy and selected area electron diffraction are performed to study the morphology and crystalline structure of the anode, respectively. The dislocation density decreased from 46.2 × 1015 m? 2 to 0.06 × 1015 m? 2 and the surface area decreased from 1.5 × 103 ?m2 to 0.05 × 103 ?m2 with cycle number increased from 1 to 102 whereas the band gap increased from 2.2 eV to 2.9 eV. The above observations are well correlated. © 2017 Elsevier Inc.Item Melt quenched vanadium oxide embedded in graphene oxide sheets as composite electrodes for amperometric dopamine sensing and lithium ion battery applications(Elsevier B.V., 2017) Moolayadukkam, M.; Shenoy, S.; Sridharan, K.; Kufian, D.; Arof, A.K.; Nagaraja, H.S.Electrochemical sensors and lithium-ion batteries are two important topics in electrochemistry that have attracted much attention owing to their extensive applications in enzyme-free biosensors and portable electronic devices. Herein, we report a simple hydrothermal approach for synthesizing composites of melt quenched vanadium oxide embedded on graphene oxide of equal proportion (MVGO50) for the fabrication of electrodes for nonenzymatic amperometic dopamine sensor and lithium-ion battery applications. The sensing performance of MVGO50 electrodes through chronoamperometry studies in 0.1 M PBS solution (at pH 7) over a wide range of dopamine concentration exhibited a highest sensitivity of 25.02 ?A mM ?1 cm ?2 with the lowest detection limit of 0.07 ?M. In addition, the selective sensing capability of MVGO50 was also tested through chronoamperometry studies by the addition of a very small concentration of dopamine (10 ?M) in the presence of a fairly higher concentration of uric acid (10 mM) as the interfering species. Furthermore, the reversible lithium cycling properties of MVGO50 are evaluated by galvanostatic charge-discharge cycling studies. MVGO50 electrodes exhibited enhanced rate capacity of up to 200 mAhg ?1 at a current of 0.1C rate and remained stable during cycling. These results indicate that MVGO composites are potential candidates for electrochemical device applications. © 2017 Elsevier B.V.Item Single step synthesis of rGO, copper oxide and polyaniline nanocomposites for high energy supercapacitors(Elsevier Ltd, 2018) Viswanathan, A.; Nityananda Shetty, A.N.Reduced graphene oxide, copper oxide and polyaniline (GCP) nanocomposites possessing energy densities close to many of Li-ion batteries are synthesized by facile in-situ single step chemical method by varying the weight percentage of each of the constituent materials. Of all the composites synthesized, the one with weight percentage of G12%: Cu2O/CuO40%: P48% (G12CP) exhibits the maximum specific capacitance of 684.93 F g?1, specific capacity of 821.91 C g?1, energy density of 136.98 W h kg?1, and power density of 1315.76 W kg?1 at the current density of 0.25 A g?1. The composite shows the retention of 84% of its initial capacitance up to 5000 cycles at a scan rate of 700 mV s?1. The electrochemical performance of G12CP is superior to the performances of other ternary composites and those of binary composites synthesized with respective weight ratios as that of G12CP composite. The potential of G12CP to act as a secondary power backup device is successfully demonstrated and the performance obtained is comparable with some of the previously reported similar works, and even superior to some others. © 2018 Elsevier LtdItem PVDF/halloysite nanocomposite-based non-wovens as gel polymer electrolyte for high safety lithium ion battery(John Wiley and Sons Inc. cs-journals@wiley.com, 2019) Khalifa, M.; Janakiraman, S.; Ghosh, S.; Adyam, A.; Anandhan, S.Gel polymer electrolyte (GPE) based on electrospun poly(vinylidene fluoride) (PVDF)/halloysite nanotube (HNT) nanocomposite non-wovens was synthesized and its suitability as a separator in lithium-ion battery (LIB) was explored. In this study, HNT played a key role in reducing the average diameter of the electrospun fibers and uplifted the porosity of the non-wovens thereby improving their electrolyte uptake. Due to a reduction in crystallinity and increased % porosity of the PVDF/HNT non-wovens, the ionic conductivity (1.77 mScm?1) and ionic transport across the separator were improved. Moreover, this GPE separator exhibited high tensile and puncture strength with negligible thermal shrinkage and a higher melting temperature compared with a commercially available separator, which is vital from the safety perspective. The cycling performance of Li/GPE/LiCoO2 cell was evaluated and it exhibited a high capacity of 138.01 mAhg?1 with 97% coulombic efficiency for the initial cycle. The cell was stable and retained its high performance with little loss in capacity even after repeated charge–discharge cycles. Such a combination of high ionic conductivity, tensile strength with low thermal shrinkage is seen to be very rare in polymer-based separators. It is noteworthy that this novel GPE outperformed the commercial separator also in the cycle performance. POLYM. COMPOS., 40:2320–2334, 2019. © 2018 Society of Plastics Engineers. © 2018 Society of Plastics EngineersItem The high energy supercapacitor from rGO/Ni(OH)2/PANI nanocomposite with methane sulfonic acid as dopant(Academic Press Inc. apjcs@harcourt.com, 2019) Viswanathan, A.; Nityananda Shetty, A.N.The low energy densities of supercapacitors limit their utilization as energy storage and energy conversion devices. To overcome this limitation, here we present a ternary nanocomposite of reduced graphene oxide (rGO)/nickel hydroxide (Ni(OH)2/polyaniline (PANI), with methane sulfonic acid as dopant, having weight percentages of 14%:14%:72% (G14NP), respectively, as an electrode material for supercapacitor. With 1 M sulfuric acid (H2SO4) as the electrolyte, the supercapacitor yields a high energy density of 120.48 W h kg?1, comparable with those of Li-ion batteries. The G14NP also exhibits good electrochemical performance with a specific capacitance of 602.40 F g?1 and a power density of 2584.83 W kg?1, at a current density of 1 A g?1. The G14NP also exhibits a promising stability of its electrochemical performances even after 16,500 cycles at a potential scan of 400 mV s?1. Remarkably, the composite performs exceptionally well at a potential window available in an aqueous electrolyte. The sustainability to high current loading while charging and its power backup application is satisfactorily demonstrated, by charging with a commercial 9 V battery. © 2019 Elsevier Inc.Item Effect of dopants on the energy storage performance of reduced graphene oxide/polyaniline nanocomposite(Elsevier Ltd, 2019) Viswanathan, A.; Nityananda Shetty, A.N.The nanocomposites comprising of reduced graphene oxide (rGO) and polyaniline (PANI) were synthesized by facile insitu single step chemical methods, with glacial acetic acid (AA) and methane sulphonic acid (MSA) as dopants for PANI. The rGO/PANI nanocomposites synthesized with the similar weight percentages of constituents exhibited better electrochemical performance in the presence of MSA than in the presence of AA, in the real two-electrode supercapacitor cell system. The nanocomposite of weight percentages of rGO-6.7%, and PANI-93.33% (GP93MSA), with MSA as dopant exhibited a remarkable feature of increase in energy storage when the number of cycles was increased. It exhibited a maximum enhancement of 237.44% in its energy storage performance, after 13600 cycles as compared to the performance before the onset of cyclic test. The high performances obtained with GP93MSA include high specific capacitance of 512.82 F g?1, specific capacity of 615.38 C g?1, energy density of 102.56 W h kg?1 and a power density of 1.8954 kW kg?1 at 1 A g?1. The energy density of the supercapacitor with GP93MSA as the electrode material, is of the same order as that of Li-ion batteries. Also, GP93MSA showcased good cyclic stability up to 23000 cycles. © 2019 Elsevier LtdItem ZnWO4/r-GO nanocomposite as high capacity anode for lithium-ion battery(Springer, 2020) Brijesh, K.; Nagaraja, H.S.The pristine ZnWO4 and ZnWO4/r-GO nanocomposite synthesized by the facile solvothermal method were tested as anode materials for lithium-ion battery. Ex situ X-ray photoelectron spectroscopy (XPS) confirms the elemental composition of the pristine ZnWO4 and ZnWO4/r-GO nanocomposite. The ZnWO4/r-GO nanocomposite shows mesoporous nature and exhibits 50.802 m2 g?1 BET specific surface area, which is higher than that of pristine ZnWO4. In addition, the electrochemical property of the pristine ZnWO4 and ZnWO4/r-GO nanocomposite investigated using 2032 half-cell reveals that GO enhances the electrochemical property of the ZnWO4. The ZnWO4/r-GO nanocomposite not only exhibits higher discharge capacity of 1158 mAh g?1 at 100 mA g?1 but also shows longer and stable cycle life at 300 mA g?1 current density. The ZnWO4/r-GO nanocomposite exhibits 80.74% capacity retention even after 500 cycles. The synergetic effect of r-GO and ZnWO4 improves the capacity, columbic efficiency, and stability of the material. The results indicate that ZnWO4/r-GO nanocomposite is an interesting anode material for Li-ion battery with higher capacity complemented with stability compared to pristine ZnWO4. [Figure not available: see fulltext.]. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Item High rate capable and high energy supercapacitor performance of reduced graphene oxide/Al(OH)3/polyaniline nanocomposite(Academic Press Inc., 2020) Viswanathan, A.; Gururaj Acharya, M.; Nityananda Shetty, A.N.The high rate capable, high energy (higher than the lead acid batteries & Nickel-cadmium batteries and comparable with Li-ion batteries) and long lasting supercapacitive performance was achieved from a ternary nanocomposite of rGO/Al(OH)3/PANI (5.88%:11.77%:82.85%) (GAlP82). The GAlP82 exhibited high cyclic stability till 47,500 cycles at 400 mV s?1, with increasing trend of specific capacitance (Cs) with increase in No. of energy storage/delivery cycles. After 41,500 cycles the GAlP82 exhibited a Cs of 490.19 F g?1, an energy density (E) of 98.03 W h kg?1 and a power density (P) of 2.2829 kW kg?1 at 1 A g?1. The GAlP82 exhibited a good rate capability by retaining 73% of Cs up to 10 A g?1 before cyclic stability study and 33% of Cs up to 23 A g?1 after 41,500 cycles; and all these impressive performances are achieved from the symmetric supercapacitor cell of GAlP82. © 2020 Elsevier Inc.Item Monoclinic Wolframite ZnWO4/SiO2 nanocomposite as an anode material for lithium ion battery(Elsevier B.V., 2020) Brijesh, K.; Dhanush, P.C.; Vinayraj, S.; Nagaraja, H.S.Herein, we report the preparation and characterization of the ZnWO4 and ZnWO4/SiO2 nanocomposite. The ZnWO4/SiO2 nanocomposite exhibits 570 mAh g?1 discharge capacity and 314 mAh g?1 charge capacity at 10 mA g?1 for the primary cycle. The increasing amount of SiO2 in the ZnWO4/SiO2 nanocomposite increases the overall performance of the composite. The synergetic effect between the ZnWO4 and SiO2 enhances the rate capability, specific capacity, cycle stability and coloumbic efficiency of the composite. The good electrochemical performance of ZnWO4/SiO2 nanocomposite makes it a promising anode for Lithium ion battery. © 2020 Elsevier B.V.Item ZnWO4/SnO2@r-GO nanocomposite as an anode material for high capacity lithium ion battery(Elsevier Ltd, 2020) Brijesh, K.; Vinayraj, S.; Dhanush, P.C.; Bindu, K.; Nagaraja, H.S.Lithium ion battery (LIB) is widely used energy storage device. Herein, we report the preparation of ZnWO4/SnO2 nanocomposite and ZnWO4/SnO2@r-GO nanocomposite via solvothermal method. The structural, elemental and morphological properties of the prepared samples are characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), high-resolution transmission electron microscopy (HR-TEM), Brunauer-Emmett-Teller (BET) measurements, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The prepared samples are tested as an anode for LIB. The ZnWO4/SnO2 (5%) nanocomposite delivers initial discharge capacity of 882 mAh g?1 at a current density of 100 mA g?1, while, the specific capacity increases with the increase of SnO2 upto 10% tested in present case. Further, ZnWO4/SnO2@r-GO nanocomposite exhibits a discharge capacity of 1486 mAh g?1 which is higher than that of ZnWO4/SnO2 nanocomposite. In addition, after 500 cycles ZnWO4/SnO2@r-GO nanocomposite exhibits 89.8% cycle life and 98% of discharge capacity retention. These results indicate that, ZnWO4/SnO2@r-GO nanocomposite is a promising anode material for LIB. © 2020 Elsevier Ltd