Hydrothermal synthesis of rutile-anatase TiO2 nanobranched arrays for efficient dye-sensitized solar cells

Rutile-anatase TiO2 nanobranched arrays were prepared in two sequential hydrothermal-synthesis steps. The morphologies and crystalline nanostructures of the samples were investigated by controlling growth time and the concentration of the titanium precursor. All samples were characterized by field-emission scanning electron microscopy and X-ray diffraction analysis. It was found that treating the surfaces of rutile TiO2 nanorods with aqueous TiCl4 solutions allows the anatase TiO2 nanobranches to grow perpendicular to the main rutile TiO2 nanorods attached to the FTO glass. Irregularly shaped, dense TiO2 structures formed in the absence of TiCl4 treatment. A light-to-electricity conversion efficiency of 3.45% was achieved using 2.3 μm tall TiO2 nanobranched arrays in a dye-sensitized solar cell. This value is significantly higher than that observed for pure rutile TiO2 nanorods. © 2014 Elsevier B.V. All rights reserved.

Preparationand Characterization of Rutile-anatase Hybrid TiO2 Thin Film by Hydrothermal Synthesis

rutile TiO2 nanorods were grown on fluorinated tin oxide (FTO) glass by hydrothermal synthesis, followed bydeposition of an anatase TiO2 film. This new method of anatase TiO2 growth avoided the use of a seed layer that is usually requiredin hydrothermal synthesis of TiO2 electrodes. The dense anatase TiO2 layer was designed to behave as the electron-generating layer,while the less dense rutile nanorods acted as electron-transfer pathwaysto the FTO glass. In order to facilitate the electron transfer,the rutile phase nanorods were treated with a TiCl4 solution so that the nanorods were coated with the anatase TiO2 film after heattreatment. Compared to the electrode consisting of only rutile TiO2, the power-conversion efficiency of the rutile-anatase hybridTiO2 electrode was found to be much higher. The total thickness of the rutile-anatase hybrid TiO2 structures were around 4.5-5.0μm, and the highest power efficiency of the cell assembled with the structured TiO2 electrode was around 3.94%..TRU

Influence of Supports on the Catalytic Activity and Coke Resistance of Ni Catalyst in Dry Reforming of Methane

The dependence of the catalytic activity and coke resistance of Ni-based catalysts on the support type was investigated in the dry reforming of methane (DRM). Catalysts were prepared using incipient wetness impregnation and analyzed using ICP-OES, BET-BJH, XRD, H2-chemisorption, H2-TPR, and CO2-TPD. DRM was performed at 600–750 °C at 144,000 mL/gcat∙h of GHSV (CH4/CO2/N2 = 1/1/1). Ni/Al2O3 and Ni/MgO catalysts formed NiAl2O4 and NiO-MgO solid solutions, respectively, owing to strong binding between the metal and support. In contrast, MgO-Al2O3 and MgAl2O4 supports suppressed NiAl2O4 and NiO-MgO solid solution formation, due to Mg addition, with high metal dispersions of 4.6 and 6.6%, respectively. In the DRM reaction, the Ni/MgO-Al2O3 and Ni/MgAl2O4 catalysts showed high CH4 conversions of 78.1 and 76.8%, respectively, compared with Ni/Al2O3 and Ni/MgO at 750 °C. A stability test was performed at 600 °C for 20 h. A coke study of the spent catalysts was performed using SEM and TGA. Alkaline-earth metal-containing catalysts Ni/MgO-Al2O3 and Ni/MgAl2O4 with strong CO2 adsorption properties showed 20 wt% reduction in carbon deposition compared to commercial catalysts. Therefore, the support and basic properties of the catalyst significantly influenced the catalyst performance and coke resistance in the DRM