328 research outputs found

    Sol-gel preparation of pure and doped TiO₂ films for the photocatalytic oxidation of ethanol in air

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    Stable sols of TiO2 were synthesized by a non-aqueous sol-gel process using titanium (IV) isopropoxide as precursor. The microstructure, optical and morphological properties of the films obtained by spin-coating from the sol, and annealed at different temperatures, were investigated using scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy and ellipsometry. The crystalline structure of the films was characterized by X-ray diffraction and their photocatalytic activity was evaluated for the oxidation of ethanol in air. The influence of the calcination temperature, pre-heat treatment and the number of layers was studied. Simultaneous thermo-gravimetric and differential thermal analysis measurements were carried out to ascertain the thermal decomposition behavior of the precursors. In order to obtain a higher photoresponse in the visible region, a series of vanadium-, niobium- and tantalum-doped TiO2 catalysts was synthesized by the same sol-gel method. For V doping two different precursors, a vanadium alkoxide and V2O5, were used. The effect on the crystallization and photocatalytic activity of the doped TiO2 films was investigated. Furthermore, to identify the effective composition of the samples, they were characterized by X-ray photoelectron spectroscopy and the surface area of the powders was measured by N-2 adsorption. The 10 wt.% doped catalysts exhibit high photocatalytic activity under visible light and among them the best performance was obtained for the sample containing Ta as dopant. The crystallite sizes are closely related to the photocatalytic activity

    Silica-based ionogels as a promising solution for all-solid-state Lithium-ion microbatteries

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    The emerging market of the Internet of Things, smart objects, wearables and others increases the demand for micro energy sources. Rechargeable lithium-ion batteries are a well-known technology for energy storage. However, safety issues and high production costs constrain progress. Electrolyte solutions based on ionic liquids (ILs) with dissolved lithium salts can be confined into inorganic porous networks forming so-called ionogels, which are investigated as solid electrolytes. Ionogels combine low hazard and good ionic conductivity. However, the growth of lithium dendrites may be observed during cycling, which reduce battery lifetime. In this project, we try to prepare a silica-ionogel to prevent dendritic growth by mechanical hindrance. The ionogel composition was studied to obtain a fast gelation and the correlation between the physical properties of the silica matrix and the electrochemical performances of the ionogel was evaluated
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