Photocatalytic performance of highly amorphous titania–silica aerogels with mesopores: The adverse effect of the in situ adsorption of some organic substrates during photodegradation

Lázár, István; Kalmár, József; Peter, Anca; Szilágyi, Anett; Győri, Enikő; Ditrói, Tamás; Fábián, István

doi:10.1016/j.apsusc.2015.08.113

Cited by 30 publications

(8 citation statements)

References 60 publications

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“…It should be noted that the bandgap energy (E g ) of the calcinated samples decreased to 3.08 eV (the standard deviation was 0.026 eV). The obtained results are consistent with the literature data that anatase as an indirect bandgap semiconductor has bandgap energy of between 3–3.2 eV [ 55 , 56 , 57 , 58 ].…”

Section: Resultssupporting

confidence: 92%

Effect of Precursor Nature and Sol-Gel Synthesis Conditions on TiO2 Aerogel’s Structure

Donėlienė¹,

Fataraitė‐Urbonienė

Rudzikas³

et al. 2021

Molecules

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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 been found for additionally nH exchanged and aged aerogel synthesized from precursor TIP. Despite the imperfections in the structure, the produced aerogels show structural and optical properties typical of the TiO2 structures mentioned in the literature.

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Section: Resultssupporting

confidence: 92%

Effect of Precursor Nature and Sol-Gel Synthesis Conditions on TiO2 Aerogel’s Structure

Donėlienė¹,

Fataraitė‐Urbonienė

Rudzikas³

et al. 2021

Molecules

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“…[1][2][3][4][5] The distinctive pore structure and the charged surface of the aerogel especially facilitates the adsorption of polar molecules and cations. [6][7][8] This generated increasing demand for thorough description of the kinetics and thermodynamics of the adsorption processes on these advanced materials. Adsorption of small molecules on mesoporous silica aerogel are fast, thus only limited kinetic and mechanistic information is available regarding these processes in the literature.…”

Section: Introductionmentioning

confidence: 99%

The pore network and the adsorption characteristics of mesoporous silica aerogel: adsorption kinetics on a timescale of seconds

et al. 2015

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Abstract. Mesoporous silica aerogel particles of ca. 5 µm in diameter can be conveniently produced by grinding in aqueous phosphate buffer at pH 7. The pores in the suspended aerogel particles are spherical and their diameter is 18 -20 nm, as measured by NMR cryoporometry.NMR diffusiometry revealed that diffusion of water is hindered inside the pores of the aerogel. In spite of steric hindrance, bulk water and pore water exchange rapidly on the millisecond timescale in the suspension, indicating a highly interconnected pore network. The adsorption of methylene blue (MB), as a model compound, was studied on the silica aerogel particles. The process was followed by on-line UV-Vis spectrophotometry after injecting the dye into the aerogel suspension. Biphasic kinetics was observed with the first process complete in ca. 80 s and the second in ca. 600 s. A detailed kinetic model was developed for the interpretation of the results. It postulates a relatively fast adsorption process with Langmuir-type kinetics, and the aggregation of aerogel particles covered by the dye on the longer timescale. The aggregates are involved in a reversible sedimentation process which actually remove MB from the suspension.

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“…Besides, some voluble information also reported recently. For example, TiO 2 film was the oxygen source for the silicon oxidation under vacuum calcinations, and with the reduction of TiO 2 [23]; methylene blue adsorption capability of TiO 2 /SiO 2 almost fully recovered by simple re-calcinations process, while the bare SiO 2 did not [7]; the photo-catalytic activity of amorphous TiO 2 raised more attention [26,27]. All these reports disclose that the active sites of microstructure remain controversial for the properties of TiO 2 and Ti-Si binary oxides.…”

Section: Introductionmentioning

confidence: 99%

Comparison study on surface depth distribution of chemical species of different nanocomposite Ti–Si binary oxides

Wang

Liu

Meng

et al. 2016

J Sol-Gel Sci Technol

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Two depths of surface of three kinds of 10 % SiO 2 Ti-Si binary oxide powder, prepared by three kinds of sol-gel processes and annealed at higher temperature, are comparatively studied by ARXPS, SEM and HRTEM. ARXPS shows that the two depths of surface for all samples enrich in Si about 38.2-63.2 % and are the mixture of TiO x (x B 2), SiO y (y B 2), Ti-O-Si, adsorbed O-containing species and C-containing species. With increasing depth, the change of Si/Ti ratio closely relates to the original structure formed in sol-gel. The surface contents of SiO 2 and Ti-O-Si linkages increase in depth for all samples. The surface of silica-supported titania and intimately mixed silica-titania has more sub-valence Ti and Si than that of silica-coated titania, but the surface of silicacoated titania has higher concentration of Ti, O and C than that of the other two. ARXPS and SEM images consistently confirm that the surface of silica-coated titania is a porous structure. HRTEM verifies that nanocrystalline anatase TiO 2 with many crystal defects has been produced in silicacoated titania.Graphical Abstract Three nanocomposite silica-titania binary oxide powders with three different structures were synthesized by three different sol-gel processes and analyzed by ARXPS, SEM and HRTEM. As it shows that the surface of silica-coated titania is a porous structure with more O and C, the surfaces of intimately mixed silicatitania and silica-supported titania, respectively, conglomerate and sinter with more suboxide Ti and Si.

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Photocatalytic performance of highly amorphous titania–silica aerogels with mesopores: The adverse effect of the in situ adsorption of some organic substrates during photodegradation

Cited by 30 publications

References 60 publications

Effect of Precursor Nature and Sol-Gel Synthesis Conditions on TiO2 Aerogel’s Structure

Effect of Precursor Nature and Sol-Gel Synthesis Conditions on TiO2 Aerogel’s Structure

The pore network and the adsorption characteristics of mesoporous silica aerogel: adsorption kinetics on a timescale of seconds

Comparison study on surface depth distribution of chemical species of different nanocomposite Ti–Si binary oxides

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