Effects of thermal treatment under different atmospheres on the spectroscopic properties of nanocrystalline TiO2

Zhang, Huarong; Xie, Chaofei; Zhang, Yanfang; Liu, Guangsheng; Li, Zonghui; Liu, Caiyun; Zhang, Fujun; Zhang, W. F.

doi:10.1063/1.2924341

Cited by 23 publications

(13 citation statements)

References 22 publications

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“…These increase the width of the defect band and in turn increase the Urbach energy. In T85, a decrease in oxygen defect density decays the Urbach tail and increases the band gap (Zhang et al 2008). Photoluminescence is a very versatile and commonly used tool to disclose the efficiency of charge carrier trapping, immigration and transfer in semiconductors.…”

Section: Resultsmentioning

confidence: 99%

Investigation of the optical property and photocatalytic activity of mixed phase nanocrystalline titania

2013

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Mixed phase nanocrystalline titania are prepared by simple sol-gel method. The physico-chemical characteristics of the prepared nanoparticles are studied with X-ray diffraction, high-resolution transmission electron microscopy, RAMAN, BET, UV-Vis, steady state and time resolved photoluminescence. X-ray diffraction and Raman spectra clearly demarcate the anatase and rutile phase as both the phases give different diffraction patterns and Raman peaks. A comparison in the band gap indicates that pure anatase and rutile phase have band gap in the UV region, whereas a mixture of these phases has lower band gap and corresponds to the visible region. Steady state and time resolved photoluminescence are employed to understand the emissivity and carrier lifetime. The photocatalytic activity is evaluated by monitoring the degradation of phenol under visible light illumination. Due to the synergistic effect of mixed anatase and rutile phases, mixed phase nanocrystalline titania exhibit superior photocatalytic activity.

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Section: Resultsmentioning

confidence: 99%

Investigation of the optical property and photocatalytic activity of mixed phase nanocrystalline titania

2013

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“…Due to the multiplicity of semiconductor TiO 2 , there have many fabrication methods to decorate the TiO 2 photoelectrode by changing TiO 2 characteristics in order to enhance cell conversion efficiency [ 9 , 10 ]. For instance, a mixture of TiO 2 nanoparticles with different size, phase composition, and morphology result in conversion efficiency because of the light scattering and the facile electron transport [ 11 , 12 ]. Alternatively, metal decoration of TiO 2 photoanodes by tailoring photoanode properties, redistributing defects, and trapping levels in the band gap enables changing the conduction band position [ 13 – 15 ].…”

Section: Introductionmentioning

confidence: 99%

Enhancement of Dye-Sensitized Solar Cells Efficiency Using Mixed-Phase TiO₂ Nanoparticles as Photoanode

Fan

Chang

2017

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Dye-sensitized solar cell (DSSC) is a potential candidate to replace conventional silicon-based solar cells because of high efficiency, cheap cost, and lower energy consumption in comparison with silicon chip manufacture. In this report, mixed-phase (anatase and rutile nanoparticles) TiO2 photoanode was synthesized to investigate material characteristics, carriers transport, and photovoltaic performance for future DSSC application. Field-emission scanning electron microscope (SEM), X-ray diffraction (XRD), photoluminescence (PL), and UV-visible spectroscopy were used to characterize mixed TiO2 particles. Subsequently, various mixed-phase TiO2 anodes in DSSC devices were measured by electrical impedance spectra (EIS) and energy efficiency conversion. The overall energy conversion efficiency of DSSC chip was improved as a result of the increase of rutile phase of TiO2 (14%) in anatase matrix. Synergistic effects including TiO2 crystallization, reduction of defect density level in energy band, longer lifetime of photoexcited electrons, and lower resistance of electron pathway all contributed to high efficiency of light energy conversion.

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“…[21][22][23][24][25] Many tactics exist to improve charge transport, such as synthesizing phase-pure semiconductor electrodes, 21,26 combining semiconductors to form composites, 22,[27][28][29] and extensively calcining metal oxides to decrease the density of oxygen vacancies. 30 Vapor post-treatment of semiconductor films can restructure the crystal framework and reduce defects, while retaining the mesoporous film framework. 31,32 This method is simple to apply, and deserves in-depth investigation.…”

Section: Introductionmentioning

confidence: 99%

Vapor treatment of nanocrystalline WO3 photoanodes for enhanced photoelectrochemical performance in the decomposition of water

Hsiao

Chen

et al. 2011

J. Mater. Chem.

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WO 3 mesoporous films were prepared using a sol-gel method to serve as the photoanode for water cleavage in a 1 M HClO 4 solution with Pt as the counter electrode. Post-treatment of the as-synthesized WO 3 film with methanol and ethanol vapors, especially with methanol, improves the photocurrent during photoelectrolysis of water. Water and hexane vapors have a deleterious influence on the WO 3 film. Scanning electron microscopy and X-ray diffraction analyses showed that treatment with methanol vapors did not alter the configuration of the nanocrystalline framework or the WO 3 mesoscopic structure. Optical absorption and W L 3 -edge X-ray absorption near-edge structural analyses also revealed that the W-ion electronic and oxidation states remained unchanged after methanol treatment. However, extended X-ray absorption fine structure analysis of the W L 3 -edge showed that the coordination number of W 6+ sites in the WO 3 film significantly increased with the methanol treatment, indicating a corresponding decrease in the defect-state density of the film. The observed increase in the coordination number resulted in a 25% increase in the electron transit rate of the WO 3 film and enhanced solar energy conversion by 32% for the photoelectrolysis of water. We conclude that post-treatment with methanol vapor remedies the defect region in nanocrystalline WO 3 films, and improves the film's electron transport performance in a photoelectrochemical cell.Scheme 1 Processes of charge transport, back transfer, and chemical interaction in a photoelectrochemical cell for water cleavage. The n-type semiconducting photoanode is positively biased for generation of O 2 gas, with corresponding H 2 gas generation on the counter electrode. V CB , V VB , V FB , and E F represent the conduction-band, valence-band, flatband, and Fermi-energy levels of the electrodes.

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Effects of thermal treatment under different atmospheres on the spectroscopic properties of nanocrystalline TiO2

Cited by 23 publications

References 22 publications

Investigation of the optical property and photocatalytic activity of mixed phase nanocrystalline titania

Investigation of the optical property and photocatalytic activity of mixed phase nanocrystalline titania

Enhancement of Dye-Sensitized Solar Cells Efficiency Using Mixed-Phase TiO₂ Nanoparticles as Photoanode

Vapor treatment of nanocrystalline WO3 photoanodes for enhanced photoelectrochemical performance in the decomposition of water

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Effects of thermal treatment under different atmospheres on the spectroscopic properties of nanocrystalline TiO2

Cited by 23 publications

References 22 publications

Investigation of the optical property and photocatalytic activity of mixed phase nanocrystalline titania

Investigation of the optical property and photocatalytic activity of mixed phase nanocrystalline titania

Enhancement of Dye-Sensitized Solar Cells Efficiency Using Mixed-Phase TiO2 Nanoparticles as Photoanode

Vapor treatment of nanocrystalline WO3 photoanodes for enhanced photoelectrochemical performance in the decomposition of water

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Enhancement of Dye-Sensitized Solar Cells Efficiency Using Mixed-Phase TiO₂ Nanoparticles as Photoanode