Charge Separation in Layered Titanate Nanostructures: Effect of Ion Exchange Induced Morphology Transformation

Riss, Alexander; Berger, Thomas; Stankic, Slavica; Bernardi, Johannes; Knözinger, Erich; Diwald, Oliver

doi:10.1002/anie.200703817

Cited by 44 publications

(45 citation statements)

References 53 publications

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“…Note that species with similar g values have also been ascribed to surface-trapped holes (Ti 4þ O 2-Ti 4þ O -) in solid anatase and rutile calcined at 1023 K. 24e However, since these signals were not found in solid anatase and rutile calcined at temperatures below 700 K, and since all the experiments were performed under air, the assignment to O 2 -is most probable. A signal similar to species VI has been observed in vacuumannealed titanate tubes 34 and in some TiO 2 materials. 35a-35d Note that this signal was also observed upon illumination of H-TNT C623 at room temperature (with 406.7 nm).…”

Section: Light-induced Epr Signals Upon Irradiation With Visiblementioning

confidence: 84%

Unraveling the Photocatalytic Activity of Multiwalled Hydrogen Trititanate and Mixed-Phase Anatase/Trititanate Nanotubes: A Combined Catalytic and EPR Study

et al. 2011

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A detailed study of the photocatalytic activity of hydrogen trititanate nanotubes (H-TNT), formed by a hydrothermal treatment, was carried out. H-TNT show a limited activity toward pyridinium chloride degradation under UV-light and even no activity under visible light. In contrast, H-TNT show activity toward the degradation of rhodamine 6G (R6G), both under UV and visible light. EPR spectroscopy is used to gain insight into this difference. UV-light excitation of H-TNT leads to the predominant formation of Ti 3þ centers by trapping of electrons at Ti sites, whereas almost no reactive oxygen-based species are formed. Upon visible light excitation of these nanotubes, no light-induced EPR signals are observed. The activity toward R6G degradation thus stems from the excitation of R6G (under both UV and visible light) and the subsequent transfer of electrons into the conduction band of TiO 2 . After a short calcination process at 623 K, the H-TNT undergo a partial phase transformation into anatase, without affecting the shape and morphology of the nanotubes, and the photocatalytic activity increases to a great extent. The EPR analysis now reveals the formation of different types of species characterized by g values larger than g e , both upon UV and visible light excitation. These reactive species, such as O 2 -and O -, are known to play an important role in the photocatalytic process.

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Section: Light-induced Epr Signals Upon Irradiation With Visiblementioning

confidence: 84%

Unraveling the Photocatalytic Activity of Multiwalled Hydrogen Trititanate and Mixed-Phase Anatase/Trititanate Nanotubes: A Combined Catalytic and EPR Study

et al. 2011

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“…9 where S stands for S 1 , S 2 or S 3 , and dye.ads stands for adsorbed dye. Through eqn (8)(9)(10)(11)(12)(13)(14) photocatalysis process takes place and consequently dye degradation.…”

Section: Application Of Titanates For Ars Dye Removal Through Photocamentioning

confidence: 99%

Reduced recombination and enhanced UV-assisted photocatalysis by highly anisotropic titanates from electrospun TiO2–SiO2 nanostructures

2014

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The surface areas of electrospun fibers/rice grain-shaped nanostructures of TiO 2 -SiO 2 composites were further enhanced after transforming them into thorn or sponge shaped titanates via selective leaching of SiO 2 , which was reported by our group previously [RSC Adv., 2012, 2, 992]. In this study, we report on their application in photocatalytic activity (PCA) when juxtaposed with photoluminescence (PL). Two defect related bands are observed in PL and their origin is discussed in relation to calcination, crystallization and nucleation effects. The relative PL intensity for sponge shapes was the lowest and hence had the lowest radiative recombination, which suggests carrier trapping at defect centers. This enables the charge carriers to migrate to the surface and participate in the PCA. The results of PCA suggested that the sponge-shaped titanate exhibits the highest degradation rate among all samples. A plausible mechanism for the differences in PCA is proposed based on the variation in the defect-densities.

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“…Low‐dimensional nanostructures such as wires, rods, belts, and tubes, having been the focus of intensive research, are expected to play an important role as both interconnects and functional units in fabricating optoelectronic, electrochemical, and electromechanical devices with nanoscale dimensions . Among various kinds of nanostructures, hydrogen titanate nanotube (HTNTs) have attracted much attention due to their high specific surface area, excellent physical properties, and fascinating potential applications since the first report of the preparation of TiO 2 ‐based nanotubes and titanate nanotubes . Because the band gap of HTNTs is extra large (>3 eV), they can only be excited by ultraviolet light (5% sunlight spectrum), which limits the utilization efficiency of natural sunlight.…”

Section: Introductionmentioning

confidence: 99%

Origin of the visible light absorption of Co²⁺ and NH₄⁺ co‐doped hydrogen titanate nanotube thin films

An¹,

Wang³

et al. 2013

Physica Status Solidi (b)

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Hydrogen titanate nanotube (HTNT) thin films were synthesized by hydrothermal method and then Co 2þ and NH þ 4 codoped hydrogen titanate nanotube (Co, N-HTNT) thin films were prepared by ion-exchange method. The Co, N-HTNT thin films exhibit strong absorption in the visible light range compared with the HTNT and NH þ 4 doped hydrogen titanate nanotube (N-HTNT) thin films. The first-principles calculations reveal that NH þ 4 doping has no effect on the visible light absorption of HTNTs. The red shift of Co, N-HTNTs is only due to the mixture of the Co 3d and O 2p states in the top of the valence band, which results in the band gap narrowing. Relative to HTNTs and N-HTNTs, both the valence band maximum (VBM) and conduction band minimum (CBM) of Co, N-HTNTs shift to lower potential based on the valence band XPS spectra. Furthermore, the up-shift of the VBM is much larger than that of the conduction band, which can result in band gap reduction explaining the origin of the visible light absorption of Co, N-HTNTs.

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Charge Separation in Layered Titanate Nanostructures: Effect of Ion Exchange Induced Morphology Transformation

Cited by 44 publications

References 53 publications

Unraveling the Photocatalytic Activity of Multiwalled Hydrogen Trititanate and Mixed-Phase Anatase/Trititanate Nanotubes: A Combined Catalytic and EPR Study

Unraveling the Photocatalytic Activity of Multiwalled Hydrogen Trititanate and Mixed-Phase Anatase/Trititanate Nanotubes: A Combined Catalytic and EPR Study

Reduced recombination and enhanced UV-assisted photocatalysis by highly anisotropic titanates from electrospun TiO2–SiO2 nanostructures

Origin of the visible light absorption of Co²⁺ and NH₄⁺ co‐doped hydrogen titanate nanotube thin films

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Charge Separation in Layered Titanate Nanostructures: Effect of Ion Exchange Induced Morphology Transformation

Cited by 44 publications

References 53 publications

Unraveling the Photocatalytic Activity of Multiwalled Hydrogen Trititanate and Mixed-Phase Anatase/Trititanate Nanotubes: A Combined Catalytic and EPR Study

Unraveling the Photocatalytic Activity of Multiwalled Hydrogen Trititanate and Mixed-Phase Anatase/Trititanate Nanotubes: A Combined Catalytic and EPR Study

Reduced recombination and enhanced UV-assisted photocatalysis by highly anisotropic titanates from electrospun TiO2–SiO2 nanostructures

Origin of the visible light absorption of Co2+ and NH4+ co‐doped hydrogen titanate nanotube thin films

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Origin of the visible light absorption of Co²⁺ and NH₄⁺ co‐doped hydrogen titanate nanotube thin films