Effect of silver doping on the phase transformation and grain growth of sol-gel titania powder

Chao, Hong; Yun, Yeoheung; Hu, Xiao-Li; Larbot, A.

doi:10.1016/s0955-2219(02)00356-4

Cited by 282 publications

(155 citation statements)

References 22 publications

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“…35 Decreasing anatase grain size ( Figure 2) results in an increase in the total boundary energy for the TiO 2 powder. The driving force for rutile grain growth is therefore increased, which promotes anatase to rutile phase transformation.…”

Section: Resultsmentioning

confidence: 98%

“…Figures 1 and 3 show that the presence of silver promotes the formation of rutile. 35 The radius of Ag + ion (126 pm) is much larger than that of the Ti 4+ ion (68 pm) and so Ag + ions cannot enter the lattice of anatase TiO 2 . 35,37 However, migration of the Ag + ions from bulk anatase grains to the anatase grain surface can occur during calcination.…”

Section: Resultsmentioning

confidence: 99%

“…For example, Chao et al reported the effect of Ag doping on the phase transformation and grain growth of sol-gel TiO 2 powder. 35 Kuo et al showed through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) that silver on TiO 2 surface coatings was easily oxidized into silver oxide (Ag 2 O) and that the addition of silver causes a reduction in photoluminescence (PL) intensity as found by PL spectroscopy. 36 This group previously showed enhanced visible light photocatalysis with Ag modified TiO 2 .…”

Section: Introductionmentioning

confidence: 99%

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A Systematic Study of the Effect of Silver on the Chelation of Formic Acid to a Titanium Precursor and the Resulting Effect on the Anatase to Rutile Transformation of TiO₂

et al. 2010

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Anatase to rutile transition in an unmodified synthetic titania usually occurs at a temperature range of 600-700°C. Various methods such as addition of metallic and nonmetallic dopants and modifying the precursor have previously been reported to influence the anatase to rutile transition temperature. In the current study, the effect of addition of increasing amounts of silver to the extent of chelation of a formate group to a titanium precursor and the resulting effects on the transformation of anatase to rutile has been studied. The addition of silver (0, 1, 3, and 5 mol %) on the anatase to rutile transformation temperature has been systematically followed by Fourier transform infrared (FTIR), Raman, X-ray diffraction (XRD), differential scanning calorimetry, and X-ray photoelectron spectroscopy (XPS) studies. From the FTIR and Raman spectroscopy studies it was observed that the incorporation of silver caused a reduction in the intensity of the COO -stretches indicating that the titania formate bridging complex is becoming weaker in the presence of silver. XRD studies indicated an early rutile formation for the silver-doped samples. XRD of the samples calcined at 700°Cshowed that 5 mol % Ag TiO 2 contained both anatase (46%) and rutile (54%), whereas the undoped sample primarily consists of anatase (95%). At 800°C all silver doped samples converted to 100% rutile and the undoped TiO 2 consisted of both anatase (55%) and rutile (45%). XPS analysis showed that Ag 0 and Ag 2 O has been formed on the surface of the titania formate complex without calcination (>100°C) indicating that photo-oxidation has occurred. FTIR, Raman, and XPS studies confirmed that the presence of silver in the xerogel before calcination may be responsible for the reduction of the titanium formate bridge. It was concluded that the presence of silver (Ag 2 O and Ag 0 ) hindered bridging ligands, which resulted in a weakened titanium gel network. This structurally weakened gel network could easily be collapsed during calcination, and it favors an early rutile formation.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Systematic Study of the Effect of Silver on the Chelation of Formic Acid to a Titanium Precursor and the Resulting Effect on the Anatase to Rutile Transformation of TiO₂

et al. 2010

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“…Noble metals can be introduced to surfaces of titania in a reduced metalic state by various methods such as electrolysis, 17 chemical reduction, 18 UV photoreduction, 19 -radiation, 20 deposition from colloids or adsorption of metal clusters. 12c, 21 Thus, the combination of titania and noble metal deposits is feasibly achieved.…”

Section: Introductionmentioning

confidence: 99%

Visible-light-induced photocatalysis through surface plasmon excitation of gold on titania surfaces

Kowalska

Mahaney

Abe

et al. 2010

Phys. Chem. Chem. Phys.

515

419

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Fifteen commercial titania (titanium(IV) oxide; TiO 2 ) powders were modified with gold by photodeposition to prepare photocatalysts that work under irradiation with light in the visible range (vis). The gold-modified titania (Au/TiO 2 ) powders were characterized by diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), scanning transmission microscopy (STEM) and X-ray powder diffraction analysis (XRD). It was shown that all tested powders could absorb visible light with an absorption maximum at localized surface plasmon resonance (LSPR) wavelengths (530-600 nm) and that the size and shape of gold nanoparticles determined absorption ranges.The photocatalytic activity of Au/TiO 2 powders was examined both under ultraviolet and vis irradiation (mainly >450 nm) for acetic acid and 2-propanol photooxidation. It was found that the activity depended strongly on gold and titania properties, such as particle size and shape, surface area and crystalline form. Under vis irradiation, large rutile particles loaded with gold particles of a wide range of sizes showed the highest level of photocatalytic activity, possibly due to greater light absorption ability in a wide wavelength range resulting from transverse and longitudinal LSPR of rod-like gold particles. Action spectrum analyses showed that visible light-induced oxidation of organic compounds by aerated gold-titania suspensions was initiated by excitation of LSPR absorption of gold. Although photocatalytic activity of nanosized gold particles under vis irradiation with a wavelength of ca. 430 nm and catalytic activity of goldmodified titania during dark reaction were also found, it was shown that the activities of 2 Au/TiO 2 particles originated from activation of LSPR of gold by light of wavelength of 530-650 nm. Participation of molecular oxygen as an electron acceptor and titania as a conductor of electrons was suggested by comparison with results obtained under deaerated conditions and results obtained using a system containing gold-deposited silica instead of gold-titania, respectively. On the basis of these results, the mechanism of visible light-induced oxidation of organic compounds on gold-titania is proposed. IntroductionTitanium(IV) oxide (TiO 2 ; titania) is an inexpensive particulate material that is readily available and has substantial photocatalytic activity, stability toward inorganic and organic compounds and non-toxicity. 1 However, one drawback of titania is that it can only be excited by ultraviolet light, i.e., with wavelengths shorter than ca. 400 nm.Therefore, only a very small portion of solar radiation (3-5%) can be utilized to drive chemical reactions. 2 Thus, extension of its absorption wavelength range to the visible region (vis) is an important issue. Another important issue is improvement of quantum efficiency, i.e., an efficiency of utilization of the photoexcited state of photocatalysts, since an electronic excited state of titania is deactivated by recombination of electrons and holes to lower qu...

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“…The most attractive process for the synthesis of TiO 2 nanoparticles is the solgel method [7][8][9][10][11][12][13][14][15][16][17][18][19]. This process involves the hydrolysis and polycondensation of a metal alkoxide Ti(OR) 4 (R=alkyl groups) precursor and subsequent formation of a gel, which after heat treatment results in a three dimensional crystalline network of linked TiO 6 octahedra [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterisation of clay-supported titania photocatalysts

Daniel

Frost

Zhu

2007

Journal of Colloid and Interface Science

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This study examines the use of laponite, a synthetic smectite, which forms exfoliated silicate layers when dispersed in water, as an inorganic support for titania nanocrystals. Titania nanocrystals are prepared prior to addition to the clay dispersion, by a sol-gel synthesis incorporating a microwave hydrothermal step. The characteristics of the resultant structure such as titania phase, crystallite size and particulate size are examined via X-Ray Diffraction (XRD), Transmission Electron Spectroscopy (TEM) and Infrared Spectroscopy.

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Effect of silver doping on the phase transformation and grain growth of sol-gel titania powder

Cited by 282 publications

References 22 publications

A Systematic Study of the Effect of Silver on the Chelation of Formic Acid to a Titanium Precursor and the Resulting Effect on the Anatase to Rutile Transformation of TiO₂

A Systematic Study of the Effect of Silver on the Chelation of Formic Acid to a Titanium Precursor and the Resulting Effect on the Anatase to Rutile Transformation of TiO₂

Visible-light-induced photocatalysis through surface plasmon excitation of gold on titania surfaces

Synthesis and characterisation of clay-supported titania photocatalysts

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Effect of silver doping on the phase transformation and grain growth of sol-gel titania powder

Cited by 282 publications

References 22 publications

A Systematic Study of the Effect of Silver on the Chelation of Formic Acid to a Titanium Precursor and the Resulting Effect on the Anatase to Rutile Transformation of TiO2

A Systematic Study of the Effect of Silver on the Chelation of Formic Acid to a Titanium Precursor and the Resulting Effect on the Anatase to Rutile Transformation of TiO2

Visible-light-induced photocatalysis through surface plasmon excitation of gold on titania surfaces

Synthesis and characterisation of clay-supported titania photocatalysts

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Product

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A Systematic Study of the Effect of Silver on the Chelation of Formic Acid to a Titanium Precursor and the Resulting Effect on the Anatase to Rutile Transformation of TiO₂

A Systematic Study of the Effect of Silver on the Chelation of Formic Acid to a Titanium Precursor and the Resulting Effect on the Anatase to Rutile Transformation of TiO₂