Zirconia Modification on Nanocrystalline Titania-Supported Cobalt Catalysts for Methanation

In this present study, the zirconia-modified different crystallite sizes of TiO2 (11, 13 and 16 nm) as support for the cobalt catalysts were investigated. The different TiO2 crystallites derived from the sol-gel method was obtained by varying the water:alkoxide molar ratio from 165 to 4 to gain the different nanocrystallite sizes of TiO2. Then, the TiO2 supports were used to yield various Co/TiO2 catalysts. It was found that the sizes of cobalt oxides species dispersed on TiO2 were corresponding to TiO2 sizes. Based on XPS study, the binding energy of Co 2p3/2 was not affected by the size of TiO2. The catalytic activity was measured via CO hydrogenation under methanation condition. In case of unmodified TiO2 support, the smaller TiO2 crystallites (Co/TiO2_11 nm) exhibited higher activity than other larger ones. Moreover, the zirconia modification also resulted in increased in activity for all samples. For both cases, it can be attributed to increased cobalt dispersion with small crystallite size of TiO2 support coupled with the zirconia modification as measured by CO chemisorption

Reactive Magnetron Sputter Deposition of Copper on TiO<inf>2</inf> Support for Photoreduction of CO<inf>2</inf> to CH<inf>4</inf>

© Published under licence by IOP Publishing Ltd. In this work, nanocrystalline Cu/TiO2 catalysts have been synthesized by using pulsed direct current (DC) reactive magnetron sputtering of Cu targets in an Ar atmosphere onto P25-TiO2 support. The oscillating bowl was used to make the uniform coating on the substrate. The Cu doping content was varied by adjusting the coating time. The thus-obtained catalysts were characterized by using the X-ray diffraction (XRD), UV-Vis spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The photocatalytic activities of all catalysts were studied via the photocatalytic reduction of CO2 and H2O to CH4 under UV irradiation, and compared with the pure TiO2 support and conventional-impregnation-made Cu/TiO2. The results showed that the photocatalytic performance of sputtering-made Cu/TiO2 catalyst was much better than the pure TiO2 support. Therefore, reactive magnetron sputtering was a promising technique for deposition of metal onto the support and use as the catalytic process

Synthesis of Cu/TiO2 catalysts by reactive magnetron sputtering deposition and its application for photocatalytic reduction of CO2 and H2O to CH4

© 2019 In the present work, a series of Cu/TiO2 catalysts were successfully synthesized by using pulsed direct current (DC) reactive magnetron sputtering of Cu targets under Ar atmosphere onto various TiO2 supports. The physiochemical properties of the catalysts were characterized by using inductive coupled plasma spectroscopy (ICP), X-ray diffraction (XRD), UV–Vis spectroscopy, N2 physisorption, transmission electron microscopy (TEM), PL spectroscopy, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of all the catalysts were studied via the photocatalytic reduction of CO2 and H2O to CH4 under UV light irradiation. The Cu/TiO2 catalysts exhibited higher photocatalytic activity than the uncoated TiO2 supports and the ones made using an impregnation technique. The electron trapping of copper species, which prolonged the electron-hole recombination process, promoted photocatalytic activity of the Cu-doped catalysts. Moreover, the specific morphologies of the Cu species deposited on TiO2 supports and the smaller change of bandgap energy of the sputter coated catalysts also resulted in an improvement of photocatalytic activity under UV light irradiation

Deposition of Pt nanoparticles on TiO2 by pulsed direct current magnetron sputtering for selective hydrogenation of vanillin to vanillyl alcohol

Pulsed direct current magnetron sputtering (PDC-MSD) was employed for the deposition of Pt nanoparticles (ca. 0.1 wt.%) on anatase TiO2 powder. According to the H2-TPR, XPS, and TEM-EDX results, the characteristics and properties of the deposited nanoparticles depended on the deposition time. During the initial deposition stage (45-90 sec), low-coordinated small spherical Pt nanoparticles were formed. Prolonging the deposition time (135-180 sec), led to the formation of larger Pt nanoparticles, which strongly interacted with the TiO2. The catalytic activities of the prepared Pt/TiO2 with different deposition times in the aqueous phase partial hydrogenation of vanillin to vanillyl alcohol ranged as follows: Pt/TiO2 MSD-45 < Pt/TiO2 MSD-90 < Pt/TiO2 MSD-180 < Pt/TiO2 MSD-135, which was in good agreement with the atomic Pt/Ti ratio and coordinated surface Pt atoms on the catalyst surface. The high catalytic activity of Pt/TiO2 MSD-135 was attributed to the presence of well-dispersed small Pt nanoparticles with more highly-coordinated Pt surface atoms deposited on the TiO2 anatase. PDC-MSD has been proven to be a more effective method for the preparation of supported metal catalysts, compared to those obtained by conventional impregnation technique

A hierarchical Ca/TiO2/NH2-MIL-125 nanocomposite photocatalyst for solar visible light induced photodegradation of organic dye pollutants in water

In this study, for the first time, the Ca/TiO2/NH2-MIL-125 nanocomposite photocatalyst was synthesized for the purpose of photodegradation of Methyl Orange (MO) and Rhodamine B (RhB) dyes under visible light irradiation. The structural and chemical properties of the nanocomposite photocatalyst were characterized through FTIR, XRD, TGA, PL, XPS, ICP-OES and UV-DRS. For the photodegradation efficiency analysis, the effect of pH (3, 5, 7, 9, and 11), photocatalyst dosage (0.1, 0.2, 0.4, 0.6, and 0.8 g L1 ), dye concentration (1–40 mg L1 ), and contact time (10–120 min) was precisely evaluated. The largest photodegradation efficiency for RhB and MO dye models was 82.87% and 86.22%, respectively, that was obtained under optimal conditions in terms of pH and photocatalyst dosage and for Ca(30%)/ TiO2/NH2-MIL-125. The photodegradation process of the dyes complied well with the first-order kinetic model. Moreover, the nanocomposite photocatalyst showed consistent photodegradation efficiency and after 6 successive cycles with fresh dye solutions, it could still perform comparably well. Taken together, Ca/TiO2/NH2-MIL-125 photocatalyst is able to show a high photodegradation efficiency for dye pollutants and optimum stability and reusability

The H-2-Treated TiO2 Supported Pt Catalysts Prepared by Strong Electrostatic Adsorption for Liquid-Phase Selective Hydrogenation

The H-2-treated TiO2 supported Pt catalysts were prepared by strong electrostatic adsorption method and tested in the liquid-phase selective hydrogenation of various organic compounds such as 3-nitrostyrene to vinylaniline (VA) and furfural to furfuryl alcohol (FA). A combination of high Pt dispersion, strong interaction of Pt-TiOx, and the presence of low coordination Pt sites was necessary for high hydrogenation activity. However, while the selectivity of VA in 3-nitrostyrene hydrogenation did not depend much on the catalyst preparation method used, the selectivity of FA in furfural hydrogenation was much higher when the catalysts were prepared by SEA, comparing to those obtained by impregnation in which the solvent product was formed, due probably to the non-acidic conditions used during Pt loading by SEA method

Improved catalytic performance of Pd/TiO2 in the selective hydrogenation of acetylene by using H-2-treated sol-gel TiO2

The anatase nanocrystalline TiO2 samples were synthesized by a sol gel method with a thermal treatment under air and H-2 atmospheres at 350 degrees C and employed as the supports for preparation of Pd/TiO2 catalysts by impregnation and electroless deposition methods. The surface Ti3+ defects on the TiO2 significantly increased when treated under H-2, compared to air, with no changes in the average crystallite size, specific surface area, and pore structure. The CO chemisorption and IR of adsorbed CO results showed that the use of H-2-treated TiO2 resulted in higher Pd dispersion and the formation of more isolated adsorption sites, hence improving the catalytic performance in terms of both acetylene conversion and ethylene selectivity