Faculty Publications
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Item Novel NiWO4-ZnO-NRGO Ternary Nanocomposites with Enhanced Photocatalytic Activity(Elsevier Ltd, 2018) Mohamed, M.; Krishna Bhat, D.A novel NiWO4-ZnO-NRGO ternary nanocomposite was efficiently synthesized via a facile, fast and easy microwave irradiation technique and its capability to photodegrade organic dye in aqueous solution was investigated. The products were characterized through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS) techniques. The photocatalytic activity was evaluated by estimating the extent of photodegradation of methylene blue (MB) under irradiation of visible light source, which showed 9 times enhancement for the ternary composites compared to that for pure NiWO4. The outcomes reveal that the novel NiWO4-ZnO-NRGO ternary nanocomposite could be a highly efficient visible light photocatalyst for the removal of environmental contaminants in wastewater. © 2018 Elsevier Ltd.Item A facile microwave approach to synthesize RGO-BaWO4 composites for high performance visible light induced photocatalytic degradation of dyes(AIMS Press Min.yu@aimspress.com, 2017) Mohamed, M.; Bhat, D.K.Photocatalysts with enhanced efficiency for environmental remediation requires an effective separation of photogenerated electron hole pairs and optimum charge carrier transport. Based on the above criteria, a cost effective, facile one-pot microwave approach was made to synthesize RGO-BaWO4 composites with excellent stability and reusability in photodegradation of methylene blue (MB) and methyl orange (MO). A series of composites with varying composition with respect to RGO was synthesized and thoroughly characterized using various techniques. The composite with 2.5% RGO-BaWO4 showed maximum efficiency under visible light irradiation. The mechanism of charge transfer and kinetics of the reaction was also studied. The interfacial/interparticle charge transfer between the narrow elliptical BaWO4 particles and RGO is found to be responsible for the increased efficiency. The photo generated holes and the superoxide radical were found to play a key role in the degradation process. The synergistic action makes RGOBaWO4 composites a promising material as high performance photocatalyst for degradation of organic dyes. © 2017 Denthaje Krishna Bhat, et al.Item Novel ZnWO4/RGO nanocomposite as high performance photocatalyst(AIMS Press Min.yu@aimspress.com, 2017) Mohamed, M.; Bhat, D.K.In this study, we report the synthesis of nanocomposite material composed of zinc tungstate (ZnWO4) and reduced graphene oxide (RGO) as photocatalyst by a simple microwave irradiation technique. The prepared nanocomposites have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FTIR), photoluminescence spectroscopy (PL) and UV-Visible spectroscopy. The photocatalytic activities of the prepared nanocomposites are evaluated in terms of the efficiencies of photodegradation of methylene blue (MB) dye in aqueous solution under visible light irradiation. The prepared nanocomposites showed excellent photodegradation efficiency compared to the commercial TiO2 under visible light irradiation. The activity of the catalyst towards methyl orange (MO) and rhodamine B (RB) was also good. Further, in view of the low cost, simple preparation method and high catalytic activity of the material, it is expected that the prepared nanocomposite can serve as an environment friendly photocatalyst for treating the large scale industrial waste waters. © 2017 Denthaje Krishna Bhat, et al.Item Enhanced photocatalytic performance of N-doped RGO-FeWO4/Fe3O4 ternary nanocomposite in environmental applications(Elsevier Ltd, 2017) Mohamed, M.; Shenoy, U.S.; Bhat, D.K.Nitrogen doped RGO- FeWO4/Fe3O4 (NRGO-FeWO4/Fe3O4) ternary nanocomposite was synthesized by rapid single step microwave irradiation approach using iron acetate, ammonium tungstate and graphene oxide as precursors. The synthesized materials were thoroughly characterized by diffraction, microscopic and spectroscopic techniques. The materials were tested for their catalytic efficiency in photo degradation of Methylene Blue (MB) dye and in reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). MB was mineralized within 100 minutes of visible light irradiation time in the presence of the ternary composite, apart from excellent stability and efficiency even after 10 consecutive cycles. The composite also had the capacity to convert 4-NP into 4-AP within 45 seconds and showed very good catalytic activity even after 20 cycles. The results revealed that ternary composite has way more efficiency than the component materials and can act as a promising catalyst for various environmental and engineering applications. © 2017 Elsevier LtdItem Electrodeposition and characterization of Ni-Mo alloy as an electrocatalyst for alkaline water electrolysis(Elsevier B.V., 2017) Shetty, S.; Mohamed, M.; Bhat, D.K.; Hegde, A.C.This work details the efficiency of Ni-Mo alloy as an electrode for water splitting application through electrodeposition method. Nano-crystalline Ni-Mo alloy coatings were deposited in the current density (c.d.) range of 1.0–4.0 A dm? 2 on a copper substrate, and were investigated for their deposit characters, and their electrocatalytic behaviours in 1.0 M KOH solution. The electrocatalytic behaviour of the coatings, in terms of their hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), were evaluated by electrochemical methods, like cyclic voltammetry (CV) and chronopotentiometry (CP). Experimental results revealed that Ni-Mo alloy electrodeposited at 1.0 A dm? 2 (38.3 wt% Mo) and 4.0 A dm? 2 (33.2 wt% Mo) shows the highest electrocatalytic tendency for HER and OER, respectively. The corrosion behaviour of Ni-Mo alloy coated at 4.0 A dm? 2 is found to be the most corrosion resistant in the same alkaline medium, compared to other coatings. The highest electrocatalytic activity of Ni-Mo alloy deposit for both HER and OER, depending on deposition c.d. was attributed to their composition (in terms of Ni and Mo content), structure and surface morphology; supported by EDXA, XRD, SEM and AFM analyses. The experimental study demonstrated that Ni-Mo alloy coatings follow Volmer-Tafel type of mechanism for HER, testified by Tafel slope analyses. © 2017 Elsevier B.V.Item RGO/ZnWO4/Fe3O4 nanocomposite as an efficient electrocatalyst for oxygen reduction reaction(Elsevier B.V., 2017) Mohamed, M.; Mutyala, S.; Mathiyarasu, J.; Bhat, D.K.Development of low cost, environmental friendly and noble metal free catalyst materials with excellent performance is essential for commercialization. In fact, this is the need of the day too. Herein, we report a facile microwave irradiation method for the synthesis of novel RGO/ZnWO4/Fe3O4 cathode catalysts for the oxygen reduction reaction (ORR) in alkaline medium. The structural and morphological features of synthesized materials are fully examined using transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM). The chemical composition and elemental analysis of the catalyst is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy techniques. Efficiency of RGO/ZnWO4/Fe3O4 catalyst material for oxygen reduction reaction (ORR) in 0.1 M KOH is reported. The activity of catalyst is determined by linear sweep voltammogram (LSV) and rotating disk electrode (RDE) measurements in O2 saturated 0.1 M KOH electrolyte. RGO/ZnWO4/Fe3O4 catalyst exhibits higher ORR activity than RGO, ZnWO4, RGO/ZnWO4 and its electrocatalytic performance is comparable to Pt/C material and is superior to it in stability and methanol tolerance. Further, it is determined that process follows a direct four electron reaction pathway. These combined results strongly signpost that RGO/ZnWO4/Fe3O4 composite can function as an economic noble metal free ORR cathode catalyst for energy applications. © 2017 Elsevier B.V.Item NiWO4-ZnO-NRGO ternary nanocomposite as an efficient photocatalyst for degradation of methylene blue and reduction of 4-nitro phenol(Elsevier Ltd, 2017) Mohamed, M.; Shenoy, U.S.; Bhat, D.K.A novel NiWO4-ZnO-NRGO ternary nanocomposite has been efficiently synthesized by decorating nitrogen doped reduced graphene oxide (NRGO) with zinc oxide and nickel tungstate nanoparticles via a facile microwave irradiation technique and its capability to catalyze photodegradation of methylene blue (MB) dye in aqueous solution and reduction of 4-nitro phenol (4-NP) to 4-amino phenol (4-AP) using sodium borohydride was explored. The as-synthesized nanocomposite was characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) analysis, energy dispersive X-ray (EDX) analysis, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and diffuse reflectance spectroscopy (DRS) techniques. The photocatalytic activity of the as-synthesized nanocomposite estimated through the photodegradation of MB under visible light irradiation showed 9 times improvement over pure NiWO4. It also showed excellent catalytic activity in reduction of 4-NP to 4-AP. The material also showed excellent stability and reusability. The entire study revealed that the novel NiWO4-ZnO-NRGO ternary nanocomposite can act as a promising bifunctional photocatalyst for environmental remediation and industrial application. © 2017 Elsevier LtdItem Electrodeposition of Ni-Mo-rGO composite electrodes for efficient hydrogen production in an alkaline medium(Royal Society of Chemistry, 2018) Shetty, S.; Mohamed, M.; Bhat, D.K.; Hegde, A.The mechanism and kinetics of the hydrogen evolution reaction (HER) on Ni-Mo-rGO composite electrodes in 1.0 M KOH solution were investigated by cyclic voltammetry (CV), chronopotentiometry (CP) and potentiodynamic polarization techniques. Ni-Mo-rGO composite coatings were deposited on a copper substrate by an electrodeposition method at a current density (c.d.) ranging from 1.0 to 4.0 A dm-2. The change in surface morphology and chemical composition was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). It was shown that the carbon content of the composite coatings was affected by c.d. With the increase in the carbon content in the Ni-Mo-rGO composite coatings, the onset potential was decreased and the exchange current density was increased during the HER. The minimum onset potential and maximum exchange current density of Ni-Mo-rGO composite coatings for the HER were -401.6 mV and 4.31 ?A cm-2. The best composite coating exhibited a maximum peak current density of -0.517 A cm-2 at -1.6 V, which is approximately 3 times better than that of the binary Ni-Mo alloy, indicating the best activity for hydrogen production. The potentiodynamic polarization measurements revealed that composite coatings are much more resistant to corrosion than binary alloy coatings. © 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item SnO2 nanoparticles functionalized MoS2 nanosheets as the electrode material for supercapacitor applications(Institute of Physics Publishing helen.craven@iop.org, 2019) Prabukumar, C.; Mohamed, M.; Krishna Bhat, D.; Udaya Bhat, K.Tin oxide (SnO2) nanoparticles undergo the volume expansion during an electrochemical cycle. This volume expansion leads to discontinuities in the form of microcracks in the electrode material. The problem of charge transportation associated with this microcracking limits the application of SnO2 in the energy storage application such as supercapacitors. The present work approached to solve this problem by incorporating the MoS2 nanosheets along with the SnO2 nanoparticles. The SnO2 nanoparticles are functionalized onto the surface of the MoS2 nanosheets by the ligand exchange process. The MoS2 nanosheets act as the support material for the SnO2 nanoparticles. The electrode material prepared using SnO2 nanoparticles and nanocomposite of SnO2 functionalized MoS2 nanosheets are tested by cyclic voltammetry and galvanostatic charge-discharge measurements. The specific capacity of the MoS2-SnO2 nanocomposite is calculated to be 61.6 F g-1 which is 4.4 fold higher than that of bare SnO2 nanoparticles. The improvement in the electrochemical performance of SnO2 is attributed to the high surface area and the charge transportation provided by the MoS2 nanosheets. © 2019 IOP Publishing Ltd.