Browsing by Subject "Copper oxides"

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    Fabrication of mesoporous CuO/ZrO2-MCM-41 nanocomposites for photocatalytic reduction of Cr(VI)
    (Elsevier, 2017) Nanda, B.; Pradhan, A. C.; Parida, K. M.
    Mesoporous nanocomposites of CuO/ZrO2–MCM-41 (CuO@ZM-41) was designed by incorporating mesoporous ZrO2 (Z) into the high surface area MCM-41 (M-41) framework followed by loading CuO by wetness impregnation method keeping Si/Zr ratio 10. The nanocomposites were studied under PXRD, N2 sorption, DRS spectra, FTIR, XPS, NMR, HRTEM and PL to evaluate structural, morphological, optical properties and also the mesoporosity nature of the samples. The photo-reduction of Cr6+ was performed over CuO@ZM-41 by varying pH, substrate concentration, and irradiation time and catalyst dose. Among all the catalysts, 2 CuO@ZM-41 was found to be efficient photocatalyst for the photo-reduction of Cr6+. Nearly 100% reduction of Cr6+ has been achieved by 2 CuO@ZM-41 within 30 min. Intra-particle mesoporosity, high surface area, presence of CuO nanorods and electron transfer properties are the key factors for enhancing the photo-reduction activity of 2CuO@ZM-41.
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    Morphological control of mesoporosity and nanoparticles within Co3O4-CuO electrospun nanofibers: quantum confinement and visible light photocatalysis performance
    (American Chemical Society, 2017-09) Pradhan, A. C.; Uyar, Tamer
    The one-dimensional (1D) mesoporous and interconnected nanoparticles (NPs) enriched composite Co3O4-CuO nanofibers (NFs) in the ratio Co:Cu = 1/4 (Co3O4-CuO NFs) composite have been synthesized by electrospinning and calcination of mixed polymeric template. Not merely the mesoporous composite Co3O4-CuO NFs but also single mesoporous Co3O4 NFs and CuO NFs have been produced for comparison. The choice of mixed polymer templates such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) for electrospinning is responsible for the formation of 1D mesoporous NFs. The HR-TEM result showed evolution of interconnected nanoparticles (NPs) and creation of mesoporosity in all electrospun NFs. The quantum confinement is due to NPs within NFs and has been proved by the surface-enhanced Raman scattering (SERS) study and the UV-vis-NRI diffuse reflectance spectra (DRS). The high intense photoluminescence (PL) spectra showing blue shift of all NFs also confirmed the quantum confinement phenomena. The lowering of PL spectrum after mixing of CuO in Co3O4 nanofibers framework (Co3O4-CuO NFs) proved CuO as an efficient visible light response low cost cocatalyst/charge separator. The red shifting of the band gap in composite Co3O4-CuO NFs is due to the internal charge transfer between Co2+ to Co3+ and Cu2+, proved by UV-vis absorption spectroscopy. Creation of oxygen vacancies by mixing of CuO and Co3O4 also prevents the electron-hole recombination and enhances the photocatalytic activity in composite Co3O4-CuO NFs. The photocurrent density, Mott-Schottky (MS), and electrochemical impedance spectroscopy (EIS) studies of all NFs favor the high photocatalytic performance. The mesoporous composite Co3O4-CuO NFs exhibits high photocatalytic activity toward phenolic compounds degradation as compared to the other two NFs (Co3O4 NFs and CuO NFs). The kinetic study of phenolic compounds followed first order rate equation. The high photocatalytic activity of composite Co3O4-CuO NFs is attributed to the formation of mesoporosity and interconnected NPs within NFs framework, quantum confinement, extended light absorption property, internal charge transfer, and effective photogenerated charge separations.