ELECTRONIC STRUCTURES OF S-DOPED ANATASE AND RUTILE TiO2

2007 ◽  
Vol 06 (01) ◽  
pp. 23-32 ◽  
Author(s):  
XIN-GUO MA ◽  
CHAO-QUN TANG ◽  
XIAO-HUA YANG
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Valence Band ◽  
Visible Light Irradiation ◽  
Electronic Structures ◽  
Density Functional ◽  
Visible Region ◽  
Light Irradiation ◽  
Band Shift ◽  
Deep Impurity

The electronic structures of S -doped TiO 2 have been carried out by first-principles calculations based on density functional theory with plane-wave ultrasoft pseudopotential method. Comparing anion doping with cation doping in anatase and rutile, we found different energy band structures and origins of photoactivity of S -doped TiO 2. For anion-doped TiO 2, new S –3p bands appear and which lie slightly above the top of the O –2p valence band. It plays a significant role in increasing absorbance in the visible region, resulting in improvement in photocatalytic activity under visible-light irradiation. For cation-doped TiO 2, the potential of the O –2p valence band shift much downwards, yielding the stronger oxidative power than that of undoped and S anion-doped TiO 2. Nevertheless, the deep impurity states in BG (bond gap) that originate from the S -dopant have negative effects on the recombination of the photoexcited electrons and holes. From our calculated results, we can explain their differences in photocatalytic activity under visible-light irradiation.

scholarly journals SOLVOTHERMAL SYNTHESIS OF BI2WO6 AND ITS PHOTOCATALYTIC ACTIVITY UNDER VISIBLE LIGHT IRRADIATION

2018 ◽  
Vol 54 (4B) ◽  
pp. 42
Author(s):  
Trinh Duy Nguyen
Keyword(s):  
Absorption Spectrum ◽  
Photocatalytic Activity ◽  
Visible Light ◽  
Visible Light Irradiation ◽  
Solvothermal Synthesis ◽  
Solvothermal Method ◽  
Visible Region ◽  
High Photocatalytic Activity ◽  
Light Irradiation ◽  
Different Temperatures

Flower-like Bi2WO6 were successfully synthesized using the solvothermal method at different temperatures and characterized by XRD, FE-SEM, and DRS. We also investigated the photocatalytic activity of Bi2WO6 for the decomposition of rhodamine B under visible light irradiation. From XRD and SEM results, the reaction temperature has significant effects on the morphologies of the samples. From DRS results, Bi2WO6 samples displayed the absorption spectrum up to the visible region and then they showed the high photocatalytic activity under visible light irradiation, as a comparison with TiO2-P25.

N,F-monodoping and N/F-codoping effects on the electronic structures and optical performances of Zn2GeO4

2015 ◽  
Vol 17 (8) ◽  
pp. 5613-5623 ◽  
Author(s):  
Yulu Li ◽  
Kaining Ding ◽  
Beisi Cheng ◽  
Yongfan Zhang ◽  
Yunpeng Lu
Keyword(s):  
Photocatalytic Activity ◽  
Optical Absorption ◽  
Visible Light ◽  
Visible Light Irradiation ◽  
Electronic Structures ◽  
Light Irradiation ◽  
Absorption Property ◽  
Optical Absorption Property

With N/F codoping, the optical absorption property of Zn2GeO4was improved under visible-light irradiation, which may promote the photocatalytic activity.

A simple method to synthesise Ag-doped TiO2 photocatalysts with different Ag0:Ag2O atomic ratios for enhancing visible-light photocatalytic activity

2017 ◽  
Vol 41 (8) ◽  
pp. 475-483 ◽  
Author(s):  
C. Chen ◽  
X. F. Lei ◽  
M. Z. Xue
Keyword(s):  
Electron Microscopy ◽  
Photocatalytic Activity ◽  
Visible Light ◽  
Visible Light Irradiation ◽  
Light Absorption ◽  
Separation Efficiency ◽  
Visible Region ◽  
Light Irradiation ◽  
Electron Hole ◽  
X Ray

Pure anatase TiO2 photocatalysts with different Ag contents were prepared via a simple sol-gel method. The as-prepared anatase Ag-doped TiO2 photocatalysts were characterised by X-ray diffraction, transmission electron microscopy, UV-Vis diffuse reflectance spectra, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, thermal gravity and differential thermal analysis, scanning electron microscopy and N2 adsorption–desorption measurements (BET). Compared with pure TiO2, Ag-doped anatase TiO2 photocatalysts exhibited not only increases in light absorption in the visible region, the separation efficiency of electron–hole pairs and surface area, but also inhibition of the titania phase transition from anatase to rutile. Photoreduction results showed that Ag-doped anatase TiO2 photocatalysts have greatly improved photocatalytic activity, compared with pure TiO2, and the reduction of Cr(VI) under visible light irradiation was much higher than that of pure TiO2. The optimum Ag content was 1.0 mol%, which led to the complete reduction of Cr(VI) under visible light irradiation (λ > 420 nm) for 4 h. The enhanced photocatalytic activity was attributed to the synergic effect of the pure anatase structure, and the increased light absorption in the visible region, separation efficiency of electron–hole pairs and atomic ratio of Ag0:Ag2O.

Enhanced Photocatalytic Activity by Silver-Modified Bismuth Vanadate

2017 ◽  
Vol 757 ◽  
pp. 88-92
Author(s):  
Cheewita Suwanchawalit ◽  
Kamonchanok Roongraung ◽  
Supat Buddee ◽  
Sumpun Wongnawa ◽  
Avinash Patil
Keyword(s):  
Methylene Blue ◽  
Photocatalytic Activity ◽  
Visible Light ◽  
Visible Light Irradiation ◽  
Visible Region ◽  
Bismuth Vanadate ◽  
Light Irradiation ◽  
Precipitation Method ◽  
Blue Dye ◽  
Vis Spectroscopy

Silver-modified bismuth vanadate (Ag-BiVO4) photocatalysts were easily prepared via the co-precipitation method. The effects of silver contents on the chemical properties of BiVO4 were evaluated. The prepared Ag-BiVO4 samples were characterized by several techniques such as X-ray diffractometry (XRD), scanning electron microscopy (SEM), and diffused reflectance UV-Vis spectroscopy (DRS). The mixed phase of monoclinic scheetlite structure and characteristic peaks of silver particles were found. Silver contents strongly affect the morphology of the prepared Ag-BiVO4 samples. DRS spectra revealed that the synthesized Ag-BiVO4 samples exhibited strong absorption in the visible region. The absorption in the visible zone is responsible for the high photocatalytic activity of Ag-BiVO4 under visible light irradiation. The photocatalytic degradation of methylene blue under visible light irradiation was studied using the BiVO4 as photocatalysts. The photocatalytic results reveal that the prepared Ag-BiVO4 samples could degrade the methylene blue dye.

Direct Sunlight Active Sm3+ Doped TiO2 Photocatalyst

2016 ◽  
Vol 855 ◽  
pp. 33-44 ◽  
Author(s):  
Binu Naufal ◽  
P.K. Jaseela ◽  
Pradeepan Periyat
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Visible Light Irradiation ◽  
Uv Light ◽  
Sol Gel ◽  
Visible Region ◽  
Light Irradiation ◽  
Significant Shift ◽  
Sem Images ◽  
Blue Solution

TiO2 and Sm3+ doped TiO2 nanocrystalline has been successfully synthesized by a modified sol-gel method. As synthesized samples of TiO2 and Sm3+ doped TiO2 were calcined at 300, 500, 700 and 800OC and characterized by various techniques such as XRD, UV/Vis Reflectance spectroscopy, FTIR, SEM-EDS and TEM. The crystallite size of Sm3+ doped TiO2 at all calcination temperature is lower than that of TiO2 due the doping Sm3+ ion and thereby induced more nanobehavior. FTIR spectroscopy confirmed the presence of Ti-O and Ti-O-Ti bond in TiO2, in Sm3+ doped TiO2 along with Ti-O and Ti-O-Ti, the presence Sm-O and Ti-O-Sm bonds are confirmed. Diffuse reflectance spectra showed that the Sm3+ doped TiO2 have a significant shift to longer wavelengths and an extension of the absorption in the visible region compared to the TiO2. SEM images confirmed that the particles are agglomerated and the particle size was decreased in the Sm3+ doped TiO2 in comparison with the TiO2. EDS analysis showed the presence of Sm3+ ion present in the lattice of TiO2 in doped sample. Finally the photocatalytic activity of TiO2 and Sm3+ doped TiO2 at various calcinations temperatures was investigated by the degradation of methylene blue solution under UV light and visible light. Doping with the samarium ions significantly enhanced the overall photocatalytic activity for MB degradation under both UV and visible light irradiation. The results showed that the Sm3+ doped TiO2 sample calcined at 700 OC shows the highest photocatalytic activity under UV light and visible light irradiation.

scholarly journals Probing Photocatalytic Characteristics of Sb-DopedTiO2under Visible Light Irradiation

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Lingjing Luo ◽  
Tianfeng Li ◽  
Xia Ran ◽  
Pan Wang ◽  
Lijun Guo
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Visible Light Irradiation ◽  
Visible Region ◽  
Light Irradiation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Degussa P25 ◽  
Antimony Chloride ◽  
Better Than

Sb-doped TiO2nanoparticle with varied dopant concentrations was synthesized using titanium tetrachloride (TiCl4) and antimony chloride (SbCl3) as the precursors. The properties of Sb-doped TiO2nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), fluorescence spectrophotometer, and Uv-vis spectrophotometer. The absorption edge of TiO2nanoparticles could be extended to visible region after doping with antimony, in contrast to the UV absorption of pure TiO2. The results showed that the photocatalytic activity of Sb-doped TiO2nanoparticles was much more active than pure TiO2. The 0.1% Sb-doped TiO2nanoparticles demonstrated the best photocatalytic activity which was better than that of the Degussa P25 under visible light irradiation using terephthalic acid as fluorescent probe. The effects of Sb dopant on the photocatalytic activity and the involved mechanism were extensively investigated in this work as well.

Cu Doped TiO2: Visible Light Assisted Photocatalytic Antimicrobial Activity and High Temperature Anatase Stability

2018 ◽  
Author(s):  
Snehamol Mathew ◽  
Priyanka Ganguly ◽  
Stephen Rhatigan ◽  
Vignesh Kumaravel ◽  
Ciara Byrne ◽  
...  
Keyword(s):  
Visible Light ◽  
Visible Light Irradiation ◽  
Density Functional ◽  
Anatase Phase ◽  
Sol Gel ◽  
Chemical Properties ◽  
Light Irradiation ◽  
Health Concern ◽  
Bacterial Inactivation ◽  
X Ray

Indoor surface contamination by microbes is a major public health concern. A damp environment is one potential sources for microbe proliferation. Smart photocatalytic coatings on building surfaces using semiconductors like titania (TiO<sub>2</sub>) can effectively curb this growing threat.<b> </b>Metal-doped titania in anatase phase has been proved as a promising candidate for energy and environmental applications. In this present work, the antimicrobial efficacy of copper (Cu) doped TiO<sub>2 </sub>(Cu-TiO<sub>2</sub>) was evaluated against <i>Escherichia coli</i> (Gram-negative) and <i>Staphylococcus aureus</i> (Gram-positive) under visible light irradiation. Doping of a minute fraction of Cu (0.5 mol %) in TiO<sub>2 </sub>was carried out <i>via</i> sol-gel technique. Cu-TiO<sub>2</sub> further calcined at various temperatures (in the range of 500 °C – 700 °C) to evaluate the thermal stability of TiO<sub>2</sub> anatase phase. The physico-chemical properties of the samples were characterised through X-ray diffraction (XRD), Raman spectroscopy, X-ray photo-electron spectroscopy (XPS) and UV-visible spectroscopy techniques. XRD results revealed that the anatase phase of TiO<sub>2</sub> was maintained well, up to 650 °C, by the Cu dopant. UV-DRS results suggested that the visible light absorption property of Cu-TiO<sub>2 </sub>was enhanced and the band gap is reduced to 2.8 eV. Density functional theory (DFT) studies emphasises the introduction of Cu<sup>+</sup> and Cu<sup>2+</sup> ions by replacing Ti<sup>4+</sup> ions in the TiO<sub>2</sub> lattice, creating oxygen vacancies. These further promoted the photocatalytic efficiency. A significantly high bacterial inactivation (99.9%) was attained in 30 mins of visible light irradiation by Cu-TiO<sub>2</sub>.

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