Synthesis and structural characteristics of nitrogen doped TiO 2 aerogels (original) (raw)
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Morphology and photocatalytic activity of TiO2 Aerogels
Research on Chemical Intermediates, 1994
In this paper we describe a methodology to form a data base that will allow us to investigate the correlation between the morphology of TiO 2 aerogels and their photocatalytic activity with respect to photodecomposition of a water soluble organic compound. We start with a qualitative theoretical argument in which we show that any functionality that involves optimization of different length scale should require some kind of ramified structure. For photocatalytic activity we need to optimize substrate and light absorptions with diffusion of products and reactants. We proceed to describe the techniques that we use to analyze and parametrize the morphology of the aerogels, using nitrogen adsorption and Small Angle Neutron Scattering. The photocatalytic activity is monitored through the photodecomposition of salicylic acid. We compare the adsorption and photodegradation of salicylic acid on the aerogels to many other forms of TiO 2 and report that under our experimental conditions the photocatalytic activity of the aerogels is superior.
Cu doped TiO 2 , Ce doped TiO 2 and undoped TiO 2 aerogels were obtain in order to compare their photocatalytic activity. The doped and undoped aerogels were obtained by sol-gel process, followed by supercritical drying and thermal treatment. XRD, ESEM, bulk elemental analysis and BET analysis were performed in order to determine the morphological and structural proprieties of doped and undoped samples. Photocatalytic activity of the undoped TiO 2 aerogel was found to be the best. Cu-and Ce-TiO 2 aerogels exhibits a close photocatalytic activity.
Effect of Precursor Nature and Sol-Gel Synthesis Conditions on TiO2 Aerogel’s Structure
2021
The aim of this investigation was to synthesize high porosity TiO2 aerogel by applying sol-gel and subcritical drying methods and to identify the influence of reagent’s nature and synthesis conditions on their structural and optical properties. Methods of XRD, FT-IR, BET, STA, SEM, and UV-vis were applied to investigate and compare the properties of synthesized TiO2 aerogels and to determine the most effective synthesis route. The structural parameters of the synthesized materials can be varied by changing the precursor type (titanium (IV), isopropoxide (TIP), or tetrabutylorthotitanate (TBOT)) and the nature of the solvent used for additional exchange (n-hexane (nH), cyclohexane (CH), or diethyl ether (DE)). All of the subcritical dried samples show the amorphous structure, which tends to crystallize into the anatase phase after calcination. The number of micro and mesopores and the specific surface area depends on the synthesis conditions. The pores with the highest diameter have ...
Fe, Ce AND Cu INFLUENCE ON MORPHO-STRUCTURAL AND PHOTOCATALYTIC PROPERTIES OF TiO2 AEROGELS
Rev. Roum. …, 2010
Fe, Ce and Cu doped TiO 2 aerogels were prepared by sol-gel method followed by supercritical drying with liquid CO 2 . Samples of aerogels, containing ~1 at% metal ions, were characterized and used as catalysts for salicylic acid photodegradation, chosen as reference water pollutant. X-ray diffraction, UV-VIS spectrophotometry and BET method were used to investigate the structural and morphological peculiarities of the obtained aerogels. The photocatalytic activity of metal doped TiO 2 aerogels were compared with that of undoped one and it was found that it depends on the metal type and its concentration. Under similar experimental conditions, Ce doped TiO 2 aerogel shows the highest efficiency for salicylic acid photodegradation.
Carbon
Monolithic structured TiO2/aerogel composites were prepared from resorcinol-formaldehyde polymer aerogel (RFA) and its carbon aerogel (RFCA) derivative. A resorcinol-formaldehyde hydrogel was synthesized in a sol-gel reaction and transformed into polymer aerogel by supercritical drying. The RFA was converted to carbon aerogel by pyrolysis at 900 °C in dry N2. Amorphous and crystalline TiO2 layers were grown from TiCl4 and H2O precursors by atomic layer deposition (ALD) at 80 °C and 250 °C, respectively, on both RFA and RFCA. The substrates and the composites were studied by N2 adsorption, TG/DTA-MS, Raman, SEM-EDX and TEM techniques. Their photocatalytic activity was compared in the UV catalyzed decomposition reaction of methyl orange dye.
Sol–gel synthesis of highly TiO2 aerogel photocatalyst via high temperature supercritical drying
Journal of Saudi Chemical Society, 2017
Nanocrystalline powders of TiO 2 xerogel and aerogel were prepared by using acidmodified sol-gel approach. For TiO 2 aerogel material (TA), the solvent was high temperature supercritically extracted at 300°C and 100 bars. However, the TiO 2 xerogel material (TX) was dried at 200°C and ambient pressure. The effects of the drying processes on the crystalline structure, phase transformation and grain growth were determined by Raman spectroscopy, SAED and Xray diffraction (XRD) analyses using Rietveld refinement method. The TiO 2 aerogel was composed of anatase crystalline structure. The TiO 2 xerogel material was composed of anatase, brookite and small amount of amorphous phase with anatase as dominant phase. The TX sample still contains a relatively high concentration of carbon than that of TA, indicating the amorphous character of TiO 2 xerogel. These materials were applied as catalyst for the degradation of indigo carmine in aqueous medium. Photo-degradation ability of TA and TX was compared to the TiO 2 commercial Degussa P25. The photo-catalytic results showed that the degradation efficiency was in the order TA > P25 > TX. The photo-degradation of indigo carmine followed pseudo first order reaction kinetics.
THE INFLUENCE OF THE HEAT TREATMENT ON THE PHOTOACTIVITY OF THE TIO2-SIO2 AEROGELS
Studia Universitatis Babeș-Bolyai. Chemia
TiO2-SiO2 aerogels were prepared by sol-gel method followed by supercritical drying with liquid CO2 and heat treatment. The structural and morphological particularities of the prepared TiO2-SiO2 aerogels were studied by means of X-ray diffraction and BET analysis. The photocatalytic activity of the TiO2-SiO2 aerogels was determined by monitoring the degradation rate of the salicylic acid. It was found that the efficiency of the TiO2-SiO2 catalyst strongly depends upon the heat treatment temperature and also on the silica content. The larger specific surface area has been achieved for the sample with the higher Si content. The heat treatment performed at 600 0 C and 700 0 C allowed the formation of anatase phase, as well as the meso-to micropore transformation. The TiO2-SiO2 (1:1 molar ratio) aerogel, heat treated at 500 0 C has the highest photocatalytic activity.