Formation of Titania Nanofibers:  A Direct Sol−Gel Route in Supercritical CO<sub>2</sub>

Sui, Ruohong; Rizkalla, Amin S.; Charpentier, Paul A.

doi:10.1021/la0505972

Cited by 77 publications

(83 citation statements)

References 33 publications

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“…Synthesis of Nanotubes: The schematic diagram of the experimental setup and details of the synthesis procedure can be found in Sui et al [14]. Reagent-grade titanium (IV) isopropoxide (TIP) (Aldrich, 97%), zirconium (IV) propoxide (ZPO) (Aldrich, 90%), acetic acid (Aldrich, 99.7%) and instrument-grade CO 2 (BOC, 99.99%) were used without further purification.…”

Section: Methodsmentioning

confidence: 99%

“…Due to these limitations, alternative processes using a green solvent such as supercritical carbon dioxide (scCO 2 ) are attractive to synthesize TiO 2 nanotubes. Previously, our group developed a direct sol-gel process to synthesize TiO 2 nanofibers, [14] where scCO 2 was used in place of an organic solvent. There are several favorable properties that make CO 2 an attractive solvent for the synthesis and processing of high-quality porous materials.…”

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confidence: 99%

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A One‐Step Approach to the Synthesis of ZrO₂‐Modified TiO₂ Nanotubes in Supercritical Carbon Dioxide

Lucky

Charpentier

2008

Advanced Materials

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Recently, considerable effort has been devoted to synthesizing materials with one-dimensional (1D) nanostructures due to their unique properties and potential applications in a diversity of applications including catalysis, high-efficiency solar cells, coatings, and sensors.[1] Particularly, titania (TiO 2 ) nanotubes are receiving considerable attention due to titania's high activity, strong oxidation capability, and chemical stability. In addition, being a low-cost material, TiO 2 is favorable for potential large-scale commercial applications. The performance of titania nanomaterials strongly relies on their crystallinity, crystallite size, crystal structure, specific surface area, thermal stability and quantum efficiency. [2,3] These properties highly depend on both the synthesis method, and the subsequent thermal-treatment technique -calcination. In some cases, doping with a second metal has been found very effective to improve the properties of TiO 2 . Zirconia has been reported as one of the most suitable dopants to enhance the thermal stability and activity of TiO 2 nanomaterials. [4][5][6] Conventionally, anodization, [7] template techniques, [8,9] hydrothermal processes, [10,11] and soft chemical processes [12] have been used to prepare TiO 2 nanotubes. However, each of these methods has limitations. The template technique requires high calcination temperatures to remove the template, resulting in a collapse of the tubular structure in the product.[12]Anodizing processes produce nanotubes with relatively-large diameters.[13] The multistep hydrothermal process requires a large amount of inorganic solvents, which may lead to environmental pollution. Due to these limitations, alternative processes using a green solvent such as supercritical carbon dioxide (scCO 2 ) are attractive to synthesize TiO 2 nanotubes. Previously, our group developed a direct sol-gel process to synthesize TiO 2 nanofibers, [14] where scCO 2 was used in place of an organic solvent. There are several favorable properties that make CO 2 an attractive solvent for the synthesis and processing of high-quality porous materials. Firstly, CO 2 is inexpensive, environmentally benign and non-flammable, with mild critical conditions (P c ¼ 73.8 bar; T c ¼ 31.1 8C), which makes this a green solvent that is suitable for both laboratory and commercial scale application. Furthermore, its physical properties such as density and solubility can be tuned by adjusting the operating temperature and pressure. Low viscosity, zero surface tension and high diffusivity of scCO 2 are also favorable in synthesizing superior ultrafine and uniform nanomaterials. In addition, scCO 2 can be easily and completely removed from products by venting; hence, no drying process is required and the porous structure can be maintained without collapsing the nanostructure. In addition, scCO 2 can be easily recycled after the pressure is diminished for potential scale-up applications. While exploring the synthesis of ZrO 2 -modified TiO 2 nanostructures by sol-gel methods in sc...

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

A One‐Step Approach to the Synthesis of ZrO₂‐Modified TiO₂ Nanotubes in Supercritical Carbon Dioxide

Lucky

Charpentier

2008

Advanced Materials

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“…Studies have also been performed on the SAS preparation of TiO 2 in both batch and semi-continuous modes using acetylacetonate and alkoxide precursors [33][34][35][36]. These studies include the use of supercritical CO 2 to induce hydrolysis of alkoxides [33] and also to facilitate the polymerisation of alkoxides with acetic acid, akin to a sol-gel process [36]. Calcination of these precursors has resulted in various TiO 2 morphologies and significantly different anatase/rutile compositions.…”

Section: Introductionmentioning

confidence: 99%

Supercritical antisolvent precipitation of TiO2 with tailored anatase/rutile composition for applications in redox catalysis and photocatalysis

Marín

Ishikawa

Bahruji

et al. 2015

Applied Catalysis A: General

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Keywords:TiO2 Supercritical CO2 Photocatalysis Direct synthesis of hydrogen peroxide Alcohol oxidation a b s t r a c t TiO 2 with tailored anatase/rutile composition has been prepared from the supercritical antisolvent (SAS) precipitation of a range of titanium alkoxides. The calcination of the SAS TiO 2 was monitored by in situ powder X-ray diffraction to determine the optimal calcination conditions for the formation of a mixed anatse/rutile phase TiO 2 . The SAS precipitated material calcined at 450 • C produced a predominantly anatase support while calcination at 750 • C resulted in a 90 wt% anatase and 10 wt% rutile TiO 2 . 5 wt% AuPd was added to the SAS TiO 2 using an impregnation technique, with exceptional dispersion of the metals being observed by transmission electron microscopy. Mean metal particle sizes were determined to be below 1 nm for both anatase and anatase/rutile SAS TiO 2 materials. These catalysts were found to be highly active for the selective oxidation of benzyl alcohol and the direct synthesis of hydrogen peroxide. In addition the anatase/rutile SAS TiO 2 was found to have comparable activity to commercial anatase/rutile mixed phase TiO 2 for the photocatalytic splitting of water for hydrogen production.

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“…TiO 2 nanotubes using the sol-gel method by templating with an anodic alumina membrane and other organic compounds or templates have also been achieved [58,59]. Earlier reports on the application of sol-gel chemistry involving an organogelator and titanium isopropoxide (Ti(OiPr) 4 ) to generate TiO 2 nanostructures [60][61][62][63][64][65][66] were directed towards accomplishments of various morphologies, however expensive and complicated procedures were involved with the drawback of metal precursors precipitation and uncontrolled product structure. Similarly, earlier reports [67][68][69][70] suggested that the crystal structure of TiO 2 nanoparticles largely depended on the preparation method.…”

Section: Introductionmentioning

confidence: 99%

Effect of organic gelator template and preparation method on the structure and morphology of nanosized polymorphic titanium oxide using the sol–gel process

et al. 2011

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The TiO 2 nanoparticles of 25-30 nm or polymorphic TiO 2 nanorods (anatase or rutile) with a diameter of 65-75 nm and a length of several micrometers were synthesized by the modified sol-gel template process. The obtained nanoparticles were uniform as suggested by the scanning and transmission electron microscopic (SEM and TEM) images; similarly, TiO 2 nanorods obtained were of single anatase or of rutile phase after calcination at lower and higher temperatures, respectively, as characterized by X-ray diffraction.

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Formation of Titania Nanofibers: A Direct Sol−Gel Route in Supercritical CO₂

Cited by 77 publications

References 33 publications

A One‐Step Approach to the Synthesis of ZrO₂‐Modified TiO₂ Nanotubes in Supercritical Carbon Dioxide

A One‐Step Approach to the Synthesis of ZrO₂‐Modified TiO₂ Nanotubes in Supercritical Carbon Dioxide

Supercritical antisolvent precipitation of TiO2 with tailored anatase/rutile composition for applications in redox catalysis and photocatalysis

Effect of organic gelator template and preparation method on the structure and morphology of nanosized polymorphic titanium oxide using the sol–gel process

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Formation of Titania Nanofibers: A Direct Sol−Gel Route in Supercritical CO2

Cited by 77 publications

References 33 publications

A One‐Step Approach to the Synthesis of ZrO2‐Modified TiO2 Nanotubes in Supercritical Carbon Dioxide

A One‐Step Approach to the Synthesis of ZrO2‐Modified TiO2 Nanotubes in Supercritical Carbon Dioxide

Supercritical antisolvent precipitation of TiO2 with tailored anatase/rutile composition for applications in redox catalysis and photocatalysis

Effect of organic gelator template and preparation method on the structure and morphology of nanosized polymorphic titanium oxide using the sol–gel process

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Formation of Titania Nanofibers: A Direct Sol−Gel Route in Supercritical CO₂

A One‐Step Approach to the Synthesis of ZrO₂‐Modified TiO₂ Nanotubes in Supercritical Carbon Dioxide

A One‐Step Approach to the Synthesis of ZrO₂‐Modified TiO₂ Nanotubes in Supercritical Carbon Dioxide