Photocatalytic activity of octahedral single-crystalline mesoparticles of anatase titanium(iv) oxide

Amano, Fumiaki; Yasumoto, Taikei; Prieto-Mahaney, Orlando-Omar; Uchida, Satoshi; Shibayama, Tamaki; Ohtani, Bunsho

doi:10.1039/b822634b

Cited by 150 publications

(128 citation statements)

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“…The octahedral structure was obtained by Amano et al using the hydrothermal reaction to synthetize a morphology with (101) facet [122]. The morphology with (001), (101), and (110) facets, as seen in the map, was obtained by Liu et al, which was synthesized using a modified hydrothermal technique in the presence of hydrogen peroxide and hydrofluoric acid solution [123].…”

Section: Anatase Tiomentioning

confidence: 99%

Effects of surface stability on the morphological transformation of metals and metal oxides as investigated by first-principles calculations

et al. 2015

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Morphology is a key property of materials. Owing to their precise structure and morphology, crystals and nanocrystals provide excellent model systems for joint experimental and theoretical investigations into surface-related properties. Faceted polyhedral crystals and nanocrystals expose well-defined crystallographic planes depending on the synthesis method, which allow for thoughtful investigations into structure-reactivity relationships under practical conditions. This feature article introduces recent work, based on the combined use of experimental findings and first-principles calculations, to provide deeper knowledge of the electronic, structural, and energetic properties controlling the morphology and the transformation mechanisms of different metals and metal oxides: Ag, anatase TiO 2 , BaZrO 3 , and α-Ag 2 WO 4 . According to the Wulff theorem, the equilibrium shapes of these systems are obtained from the values of their respective surface energies. These investigations are useful to gain further understanding of how to achieve morphological control of complex three-dimensional crystals by tuning the ratio of the surface energy values of the different facets. This strategy allows the prediction of possible morphologies for a crystal and/or nanocrystal by controlling the relative values of surface energies.

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Section: Anatase Tiomentioning

confidence: 99%

Effects of surface stability on the morphological transformation of metals and metal oxides as investigated by first-principles calculations

et al. 2015

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“…In addition, the difference in surface energies of the conduction and valence bands of different crystal facets of titania can promote the separation of electrons and holes [12]. The shape of an anatase titania single crystal, which determines the type of the exposed crystal facet, has recently been recognized as a potential key factor influencing photocatalytic efficiency and selectivity [13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Decahedral-shaped anatase titania photocatalyst particles: Synthesis in a newly developed coaxial-flow gas-phase reactor

Janczarek

Kowalska

Ohtani

2016

Chemical Engineering Journal

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Decahedral-shaped anatase particles (DAPs) were prepared by a gas-phase process consisting of titanium(IV) chloride oxidation. The use of a coaxial-flow gas-phase reactor resulted in high reaction yield (ca. 70%) and good reproducibility of DAPs production. The influence of controlled and resultant preparation parameters on the process course and on DAPs properties (such as specific surface area, particle size and particle morphology) is discussed in detail.Correlations between preparation parameters and product properties indicated the best conditions for obtaining DAPs of high quality and thus with a high level of photocatalytic activity for various reaction systems.Keywords: anatase titania, decahedral-shaped particles, gas-phase synthesis, coaxial-flow reactor, photocatalytic activityconcentration of TiCl 4 vapor in gas phase (vol%) amount of powder collected from the glassfiber filter (g) length of the reaction zone (m) line speed ratio of reactant gases internal pressure (kPa) particle aspect ratio primary particle size (nm) particle shape distribution (%) particle size heterogeneity radial distance (m) reaction tube radius (m) Reynolds numbersecondary particle size (nm) specific surface area (m 2 g -1 ) amount of powder collected from the reaction tube (g) furnace temperature (K) residence time (s) average volumetric flow rate of the gas mixture (m 3 s -1 ) volumetric flow rate of argon (m 3 s -1 ) volumetric flow rate of oxygen (m 3 s -1 ) volumetric flow rate of TiCl 4 vapor (m 3 s -1 ) volumetric flow rate of TiCl 4 liquid (m 3 s -1 ) viscosity of the gas mixture (Pa s) density of the gas mixture (kg m -3 )

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“…P25 is a well-known standard photocatalyst displaying high photocatalytic efficiency for H 2 evolution in the presence of supported Pt nanoparticles, as a cocatalyst, and sacrificial electron donors such as alcohols. 8,9 The anatase-rich P25 was calcined at 900°C for 2 h in air to induce phase transformation from anatase to rutile. The resulting sample is denoted as P900.…”

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Photocatalytic Activity of Rutile Titania for Hydrogen Evolution

Amano¹,

Nakata²,

Ishinaga³

2014

Chemistry Letters

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Herein, we demonstrate the high photocatalytic activity of rutile particles for H 2 evolution from aqueous ethanol solution. The rutile particles were prepared by successive calcination at 900°C and H 2 reduction treatment at 700°C of commercial anatase-rich TiO 2 powder, Evonik/Degussa P25. Photocatalytic water splitting to generate H 2 and O 2 using oxide photocatalysts has potential for large-scale fuel production from solar energy.1 Titanium dioxide has been a widely studied photocatalyst since the photoelectrolysis of water by singlecrystal rutile TiO 2 electrode was reported in 1969.2 However, a feasible design concept for highly efficient photocatalysts, including conventional TiO 2 photocatalysts, for water splitting has yet to be developed.The photocatalytic activity of rutile is considered to be lower than that of anatase.36 Rutile particles are generally larger than anatase particles, as rutile is the thermodynamically stable phase of TiO 2 . 4 The low photocatalytic activity might be due to the small specific surface area of rutile particles. Rutile is also reported to exhibit higher rates of recombination compared to those displayed by anatase. 3 The difference in the energy levels of anatase and rutile is also important for photocatalytic water splitting. Electrochemical studies indicate that the flat band potential of rutile (001) is more positive than that of anatase (101) by 0.2 V.7 This indicates that the reducing ability of rutile is lower than that of anatase. Considering the band gaps of anatase (3.2 eV) and rutile (3.0 eV), the position of the valence band maxima are similar, as shown in Figure 1. The energy level of the conduction band minimum of rutile is comparable to the redox potential of H + /H 2 (0 V vs. SHE); thus, nearly no overpotential is available for H 2 evolution. 7 In contrast, there is no evidence that the photoexcited electrons in the conduction band of rutile are thermodynamically inefficient for the reduction of water to H 2 . A better understanding is required for evaluating the photocatalytic activity of rutile TiO 2 particles in H 2 evolution.Herein, we examined the photocatalytic activity of rutile particles for H 2 evolution from aqueous ethanol solution. The rutile particles were prepared from commercial anatase-rich TiO 2 , Evonik/Degussa P25 (Nippon Aerosil, Yokkaichi, Japan), as a precursor. P25 is a well-known standard photocatalyst displaying high photocatalytic efficiency for H 2 evolution in the presence of supported Pt nanoparticles, as a cocatalyst, and sacrificial electron donors such as alcohols. 8,9

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Photocatalytic activity of octahedral single-crystalline mesoparticles of anatase titanium(iv) oxide

Cited by 150 publications

References 21 publications

Effects of surface stability on the morphological transformation of metals and metal oxides as investigated by first-principles calculations

Effects of surface stability on the morphological transformation of metals and metal oxides as investigated by first-principles calculations

Decahedral-shaped anatase titania photocatalyst particles: Synthesis in a newly developed coaxial-flow gas-phase reactor

Photocatalytic Activity of Rutile Titania for Hydrogen Evolution

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