Microstructures and Photocatalytic Properties of S Doped Nanocrystalline TiO<sub>2</sub>Films

Peng, Xue-Lei; Yao, Mingming; Li, Fang; Sun, X.

doi:10.1080/02726351.2010.551711

Cited by 14 publications

(2 citation statements)

References 21 publications

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“…The literature is populated with contradictory arguments about whether sulfated titania enhances photocatalytic activity or not. The narrowing of the band gap clearly leads to enhanced activity under visible light; however, some reports demonstrate higher photocatalytic activity under UV light for sulfur-doped titania, 31,50,82 while others show less photooxidation activity under UV light compared to pure titania. 34,[36][37][38]51,52,75 We propose that the ability to control whether sulfur atoms substituted on Ti sites act as electron or hole traps by tuning the non-stoichiometry of the TiO 2+x titania lattice introduces new opportunities to optimize electron and hole dynamics in photocatalysis using sulfated titania.…”

Section: Discussionmentioning

confidence: 99%

Direct Evidence for Sulfur-Induced Deep Electron and Hole Traps in Titania and Implications for Photochemistry

Chokanlu

Mahdavi‐Shakib

et al. 2023

J. Phys. Chem. C

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Numerous studies show that sulfating titania narrows its band gap, facilitating longer-wavelength photochemistry, but there are contradictory reports on whether this improves or degrades UV photocatalysis and whether reactions proceed via electron-or hole-mediated pathways. The widely proposed role of sulfur is that it induces deep electron traps, which increase hole lifetimes. There is, however, no direct evidence for unoccupied states deep in the band gap. By contrast, transient absorption spectroscopy indicates that sulfur induces hole traps. We present experiments on sulfur-free and sulfated titania in which dissociation of hydrogen generates electrons that fill the lowest unoccupied states. The energy of these electrons relative to the conduction band minimum (CBM) was measured with diffuse reflectance spectroscopy in the infrared and UV−vis ranges. For all commercial sulfur-containing anatase materials, conversion of tridentate sulfate species into sulfur substituted on lattice sites occurred under highly oxidizing conditions above 400 °C and led to partially unoccupied states ∼2.8 eV below the CBM. We assign this deep trap state to sulfur atoms substituted on a titanium lattice site with a formal charge of S 5+ in non-stoichiometric TiO 2+x , based on agreement between the experiment and the predicted UV− vis spectrum of Harb, Sautet, and Raybaud, using HSE06 density functional perturbation theory. Our band structure calculations demonstrate that titanium vacancies (or excess oxygen) are necessary to create partially unoccupied states, and X-ray diffraction Rietveld analysis confirms the existence of these vacancies. The partial occupancy of these states, along with sulfur's ability to switch oxidation states, explains their role as both electron (S 5+ + e − → S 4+ ) and hole (S 5+ + h + → S 6+ ) traps, reconciling previous work. We discuss how relative rates of electron vs hole trapping can enhance or degrade activity depending on the pathway and the TiO 2+x non-stoichiometry. We consider how increasing the dopant concentration can induce band bending or pin the Fermi level and shift the redox reactions that are thermodynamically accessible.

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Section: Discussionmentioning

confidence: 99%

Direct Evidence for Sulfur-Induced Deep Electron and Hole Traps in Titania and Implications for Photochemistry

Chokanlu

Mahdavi‐Shakib

et al. 2023

J. Phys. Chem. C

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“…Peng et al 2012;Vereb et al 2013). These reactions are of particular interest as a result of their ability to use the solar energy (Hamadanian et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Structural and Photocatalytic Activity of Mesoporous N-Doped TiO₂with Band-to-Band Visible Light Absorption Ability

Janitabar-Darzi¹

2014

Particulate Science and Technology

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White colored N-doped TiO 2 and a neat TiO 2 powder were synthesized via sol-gel method. Prepared samples were characterized by means of x-ray diffractions, Brunauer-Emmet-Teller and Barrett-Joyner-Halenda methods, x-ray photoelectron spectroscopy, ultraviolet-visible analysis, scanning electron microscopy, and energy dispersive x-ray spectroscopy. Both of the N-doped TiO 2 and neat TiO 2 consisted of anatase phase of titania with mesoporous nature and according to XPS analysis prepared N-doped TiO 2 is a substitutional nitrogen containing sample. The band gap of N-doped TiO 2 and neat TiO 2 were estimated from ultraviolet-visible spectroscopy data to be 2.7 and 3.2 eV, respectively. Prepared substitutional N-doped TiO 2 featured steep light absorption edge with an approximately parallel characteristic of its absorption edge to that neat TiO 2 . This is due to its band-toband visible light absorption ability. Synthesized N-doped TiO 2 had a large surface area value of 193 m 2 =g and high photon absorption ability causing superior photocatalytic properties towards Congo red azo dye compared to neat TiO 2 either under ultraviolet or visible light illumination.

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Enhanced Photocatalytic Activity of Co Surface Doped Nanocrystalline TiO2-SiO2 Composite Films

Zhao

Yao

Feng

et al. 2012

Water Air Soil Pollut

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Microstructures and Photocatalytic Properties of S Doped Nanocrystalline TiO₂Films

Cited by 14 publications

References 21 publications

Direct Evidence for Sulfur-Induced Deep Electron and Hole Traps in Titania and Implications for Photochemistry

Direct Evidence for Sulfur-Induced Deep Electron and Hole Traps in Titania and Implications for Photochemistry

Structural and Photocatalytic Activity of Mesoporous N-Doped TiO₂with Band-to-Band Visible Light Absorption Ability

Enhanced Photocatalytic Activity of Co Surface Doped Nanocrystalline TiO2-SiO2 Composite Films

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Microstructures and Photocatalytic Properties of S Doped Nanocrystalline TiO2Films

Cited by 14 publications

References 21 publications

Direct Evidence for Sulfur-Induced Deep Electron and Hole Traps in Titania and Implications for Photochemistry

Direct Evidence for Sulfur-Induced Deep Electron and Hole Traps in Titania and Implications for Photochemistry

Structural and Photocatalytic Activity of Mesoporous N-Doped TiO2with Band-to-Band Visible Light Absorption Ability

Enhanced Photocatalytic Activity of Co Surface Doped Nanocrystalline TiO2-SiO2 Composite Films

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Microstructures and Photocatalytic Properties of S Doped Nanocrystalline TiO₂Films

Structural and Photocatalytic Activity of Mesoporous N-Doped TiO₂with Band-to-Band Visible Light Absorption Ability