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Item Chemically prepared Polypyrrole/ZnWO 4 nanocomposite electrodes for electrocatalytic water splitting(Elsevier Ltd, 2019) Brijesh, K.; Bindu, K.; Shanbhag, D.; Nagaraja, H.S.ZnWO 4 , PPy, and PPy/ZnWO 4 nanoparticles were prepared using chemical synthesis. The structural, compositional and morphological properties of the prepared samples have been investigated using XRD, FTIR, SEM, and HRTEM respectively. The powder XRD reveals the monoclinic wolframite structure for both ZnWO 4 and PPy/ZnWO 4 nanocomposite. SEM confirms the wrapping of ZnWO 4 with PPy. The electrodes of ZnWO 4 , PPy, and PPy/ZnWO 4 have been tested as bifunctional electrocatalyst towards HER and OER using constant current chronopotentiometry (CP) and Linear Sweep Voltammetry (LSV). The electrochemical surface area and the electrocatalytic activity PPy/ZnWO 4 nanocomposite towards HER and OER are greater than that of pure ZnWO 4 and PPy. The Tafel slope of PPy/ZnWO 4 nanocomposite is 76 and 84 mV dec ?1 in 0.5 M H 2 SO 4 and 1 M KOH at room temperature for HER and OER respectively. The results suggest that PPy/ZnWO 4 nanocomposite is a good candidate for the bifunctional electrocatalyst for water splitting. © 2018 Hydrogen Energy Publications LLCItem Lower Band Gap Sb/ZnWO4/r-GO Nanocomposite Based Supercapacitor Electrodes(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Brijesh, K.; Nagaraja, H.S.Sb/ZnWO4/r-GO nanocomposite has been prepared by a single step solvothermal method. The crystal structure of the prepared nanocomposite has been characterized using a powder x-ray diffractometer (XRD). The optical properties of the prepared nanocomposite were studied using UV–visible spectroscopy and photoluminescence. The energy band gap of 3.52 eV is obtained for the ZWS-5 nanocomposite using Tauc plots. For both Sb/ZnWO4 and Sb/ZnWO4/r-GO nanocomposite XRD shows the monoclinic Wolframite structure. The supercapacitor performance of the prepared samples was carried out using electrochemical techniques such as cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The nanocomposite ZWS-5 exhibits a specific capacitance of 102 F/g, which is higher than pristine ZWS specific capacitance of 64 F/g. Both ZWS and ZWS-5 electrodes show good capacitance retention proficiency even after 1000 cycles. © 2019, The Minerals, Metals & Materials Society.Item Dual electrochemical application of r-GO wrapped ZnWO4/Sb nanocomposite(Institute of Physics Publishing helen.craven@iop.org, 2019) Brijesh, K.; Bindu, K.; Amudha, A.; Nagaraja, H.S.ZnWO4/Sb nanorods and r-GO-ZnWO4/Sb nanocomposite have been prepared using a single step solvothermal method. The prepared nanocomposites have been characterized using x-ray diffractometer (XRD), Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscope (HR-TEM), Raman and Brunauer-Emmett-Teller (BET). The x-ray photoelectron spectroscopy (XPS) technique was used to determine the elemental composition of ZWS-5 (5 mg r-GO-ZnWO4/Sb) composite. The XRD reveals the monoclinic wolframite structure of ZnWO4/Sb and r-GO-ZnWO4/Sb. SEM and HRTEM confirms that the ZnWO4/Sb has been decorated on the r-GO sheets. The electrochemical performance of the prepared samples towards the Hydrogen Evolution Reaction (HER) and dopamine sensing has been tested using electrochemical techniques. Onset potential of 265 mV @10 mA cm-2, lower Tafel slope (95 mV dec-1), high electrochemical surface area (1383.216 m2g-1) and high specific site density (18.551 06 × 1021 g-1) of ZWS-5 reveals the high electrocatalytic activity of the composite towards HER. Chronoamperometric dopamine sensing shows that ZWS-5 has the superior sensing performance with highest specific sensitivity (723 ?A ?M-1 ?g-1), lowest limit of detection (0.9624 ?M), along with a good selectivity. Results suggest that the r-GO-ZnWO4/Sb nanocomposite is a good candidate for the HER and electrochemical dopamine sensor. The incorporation of r-GO nanosheets with ZnWO4/Sb (ZWS) nanorods enhances the specific and electrochemical surface area, which accounts for the high electrocatalytic activity of the composite. © 2019 IOP Publishing Ltd.Item 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 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 LtdItem GeO2/ZnWO4@CNT nanocomposite as a novel anode material for lithium-ion battery(Springer, 2020) Brijesh, K.; Nagaraja, H.S.Single-walled carbon nanotube (SWCNT) wrapped GeO2/ZnWO4 nanocomposite was prepared by single-step solvothermal method. In this work, GeO2/ZnWO4 nanocomposites were prepared by varying the molar percentage of GeO2 and by further adding SWCNT for the composite to boost the electrochemical performance. The prepared GeO2/ZnWO4 nanocomposites and GeO2/ZnWO4@CNT nanocomposite are used as anode material for lithium-ion battery (LIB). As expected, GeO2/ZnWO4@CNT nanocomposite exhibits higher capacities and good rate capability than the GeO2/ZnWO4 nanocomposite. The GeO2/ZnWO4@CNT nanocomposite exhibits 930 mAh g?1 discharge capacity and 533 mAh g?1 charge capacity for the initial cycle at 100 mAh g?1 in the voltage range of 0.01–3 V (vs. Li+/Li). Even at high current density of 500 mAh g?1, GeO2/ZnWO4@CNT nanocomposite shows 231 mAh g?1 and 257 mAh g?1 charge/discharge capacity which are higher than that of GeO2/ZnWO4 nanocomposite. The GeO2/ZnWO4@CNT nanocomposite delivers 75.8% capacity retention and 100% coulombic efficiency even after 400 cycles at 300 mAh g?1. These results direct that GeO2/ZnWO4@CNT nanocomposite is a good negative electrode for lithium-ion battery. [Figure not available: see fulltext.]. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.