Faculty Publications

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Author: search.filters.author.Nagaraja, H.S.Subject: search.filters.subject.Electrocatalytic activity

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    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.
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    Influence of cations in MFe2O4 (M: Fe, Zn, Ni, Sn) ferrite nanoparticles on the electrocatalytic activity for application in hydrogen peroxide sensor
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Bindu, K.; Nagaraja, H.S.
    Hydrothermally prepared MFe2O4 (M: Fe, Zn, Ni and Sn) nanoparticles have been characterized by XRD, SEM and BET. The ferrite nanoparticles have been tested for their electrocatalytic activity and application towards the reduction and sensing of hydrogen peroxide using cyclic voltammetry and chronoamperometry techniques. ZnFe2O4 and SnFe2O4 reveal superior H2O2 sensing performance than Fe3O4 and NiFe2O4, which can be attributed to the lower redox potential of Sn2+/Sn4+ couple, lower charge-transfer resistance and higher specific surface area. ZnFe2O4 and SnFe2O4 have a sensitivity of 4.411 and 3.915 ?AmM-1 ?g-1, respectively, which is greater than that of Fe3O4 (0.434 ?AmM-1 ?g-1) and NiFe2O4 (0.644 ?AmM-1 ?g-1). SnFe2O4 has the lowest limit of detection (2.6 (M) with good selectivity towards H2O2 in the presence of other interference agents. © 2019 IOP Publishing Ltd.
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    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.