Faculty Publications
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Item Novel RGO-ZnWO4-Fe3O4 nanocomposite as high performance visible light photocatalyst(Royal Society of Chemistry, 2016) Mohamed, M.M.J.; Shenoy, U.S.; Bhat, D.K.A novel RGO-ZnWO4-Fe3O4 nanocomposite is synthesized by a microwave irradiation method and its catalytic activity for the photo degradation of Methylene Blue (MB) is investigated. The prepared nanocomposites are characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), Raman spectroscopy, photoluminescence spectroscopy (PL) and UV-visible spectroscopy. The visible light photocatalytic activities of the prepared nanocomposites are investigated using a MB dye solution. It is noteworthy that RGO-ZnWO4-Fe3O4 nanocomposites exhibited relatively high photocatalytic activity compared to ZnWO4-RGO and pure ZnWO4 on MB in aqueous solution. This enhanced rate is due to the ability of the graphene in the RGO-ZnWO4-Fe3O4 composite to support carrier exploitation efficiently by tolerating the photo excited electron-hole pairs and thus encouraging oxidative degradation of the pollutants. This work could be extended to other organic pollutants as well and could provide new insights into ternary nanocomposites as high performance photocatalysts and their application in waste water treatment. © 2016 The Royal Society of Chemistry.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 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 Novel NRGO-CoWO4-Fe2O3 nanocomposite as an efficient catalyst for dye degradation and reduction of 4-nitrophenol(Elsevier Ltd, 2018) Mohamed, M.M.J.; Shenoy, S.; Bhat, D.K.Novel NRGO-CoWO4-Fe2O3 (N-doped reduced graphene oxide-cobalt tungstate-iron oxide) ternary nanocomposite was prepared by using simple microwave method. The synthesized materials were thoroughly characterized by X-ray diffraction (XRD) studies, Brunauer-Emmett-Teller (BET) analysis, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, photoluminescence (PL) and UV-Visible spectroscopy. The nanocomposite was studied for its catalytic activity in degradation of methylene blue (MB) and reduction of 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP). The observed results of catalytic efficiency and rate constants indicated that the NRGO-CoWO4-Fe2O3 nanocomposite can perform as an excellent catalyst compared to other composite materials. The detailed experimental study revealed that this ternary nanocomposite shows a great promise as a candidate for various environmental applications. © 2018 Elsevier B.V.Item Tuning the Photocatalytic Activity of SrTiO3 by Varying the Sr/Ti Ratio: Unusual Effect of Viscosity of the Synthesis Medium(American Chemical Society service@acs.org, 2018) Bantawal, H.; Shenoy, U.S.; Bhat, D.K.SrTiO3 nanostructures were successfully synthesized in various alcohols as cosolvent as well as surfactant by a facile solvothermal method. The as-synthesized catalysts were characterized by X-ray diffraction technique, scanning electron microscopy, energy-dispersive X-ray analysis, Brunauer-Emmett-Teller analysis, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The possible formation mechanism of SrTiO3 in the presence of these alcohols is discussed, and the effect of these alcohols on the structure, Sr/Ti atomic ratio, and optical properties is related to the photocatalytic activity. First principles calculations were made use of to determine the effect of defects on the electronic structure and the band gap. The photocatalytic activity of these catalysts was evaluated by taking methylene blue as a model pollutant under visible light irradiation. It was found that the photocatalytic activity of ethanol-mediated SrTiO3 was found to be higher than the other samples because of the synergistic effect of high surface area and lesser defects. © 2018 American Chemical Society.Item Solar active ZnO–Eu2O3 for energy and environmental applications(Elsevier Ltd, 2020) Subramanian, S.; Kumaravel, K.; K, K.; Bhat, D.K.; Iyer Sathiyanarayanan, K.; Swaminathan, M.ZnO–Eu2O3 nanocomposite was fabricated by a simple hydrothermal route. This material forms a potential class of photocatalysts in which the increased absorption behaviour in ZnO–Eu2O3 is expected to couple with the existing characteristics of Eu2O3 and ZnO materials. ZnO–Eu2O3 was characterized using surface analytical (SEM, EDS, HR-TEM, AFM, XRD) and spectroscopic techniques (XPS, DRS,PL). From the XRD patterns, formation of well-crystallized cubic Eu2O3 and hexagonal wurtzite phase of ZnO were inferred. Presence of nanoflake like structure with hexagonal ZnO and cubical Eu2O3 is shown by SEM pictures. ZnO–Eu2O3 possesses higher UV and visible absorption than Eu2O3 and ZnO. ZnO–Eu2O3 produces larger methanol oxidation current indicating its anodic catalytic efficiency in direct methanol fuel cells (DMFCs). This reveals higher electrocatalytic activity of ZnO–Eu2O3 than ZnO. It is observed that at ?1.6 V, cathodic current density (ipc) of ZnO–Eu2O3 (?103.17 mA cm?2) for Hydrogen evolution reaction (HER) is more than five times of ZnO (?18.19 mA cm?2) and the hydrogen evolved with ZnO–Eu2O3is 15.6 mL, which is higher than that of ZnO (6.8 mL). This indicates the superior catalytic property of ZnO–Eu2O3 in water splitting. This catalyst exhibited higher catalytic activity of 99.2% in the photodegradation of Rhodamine B (Rh-B) with natural sunlight in 75 min under neutral pH, whereas Eu2O3 and ZnO produced 60 and 82% degradations in the same time. Degradation quantum efficiency by ZnO–Eu2O3 is larger than ZnO and Eu2O3. ZnO–Eu2O3 was stable and reusable. The multifunctionality of this catalyst makes it suitable for energy and environmental applications. © 2020 Elsevier B.V.Item Copper doping induced band structure and morphology transformation in CaTiO3 for textile dye photodegradation applications(Elsevier Ltd, 2024) Shenoy, U.S.; Uma, P.I.; Bhat, D.K.Semiconductor metal oxides with a wide bandgap like CaTiO3 can be exploited into an efficient visible light photocatalyst via cation doping. The type of dopant and the site of doping is known to greatly influence the photocatalytic activity of a material. Based on the intricacies of the density functional theory electronic structure study, we delve into the optimization of one-pot solvothermal synthesis to obtain Cu doped CaTiO3 nanocuboids. Doping of copper not only resulted in change in the electronic structure of the material but also led to change in the morphology. The uneven nanostep architecture resulted in increase in the surface area of the catalyst, which led to more active sites for the adsorption of the dyes and subsequent degradation. The reduced band gap and decreased recombination of charge carriers made the copper doped calcium titanate an efficient photocatalyst for degradation of both cationic (99.7% degradation of MV dye in 120 minutes) and anionic (99.8% degradation of RB in 45 minutes) dyes. © 2024 Elsevier B.V.