scholarly journals Hydrogen treated anatase TiO2: a new experimental approach and further insights from theory

2016 ◽  
Vol 4 (7) ◽  
pp. 2670-2681 ◽  
Author(s):  
Manan Mehta ◽  
Nisha Kodan ◽  
Sandeeep Kumar ◽  
Akshey Kaushal ◽  
Leonhard Mayrhofer ◽  
...  
Keyword(s):  
Visible Light ◽  
Ab Initio ◽  
Light Absorption ◽  
Photoelectron Spectroscopy ◽  
Experimental Approach ◽  
Anatase Tio2 ◽  
Hydrogen Annealing ◽  
Visible Light Absorption ◽  
X Ray

Vacuum hydrogen annealing of TiO2 leads to increased visible light absorption. The origin thereof was revealed by ab initio calculations and X-ray photoelectron spectroscopy.

scholarly journals Exfoliated Molybdenum Disulfide Encapsulated in a Metal Organic Framework for Enhanced Photocatalytic Hydrogen Evolution

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 89 ◽  
Author(s):  
Ren Ren ◽  
Huilei Zhao ◽  
Xiaoyu Sui ◽  
Xiaoru Guo ◽  
Xingkang Huang ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Visible Light ◽  
Light Absorption ◽  
Photoelectron Spectroscopy ◽  
Metal Organic Framework ◽  
Visible Light Absorption ◽  
X Ray ◽  
Metal Organic ◽  
Direct Band ◽  
Bulk Mos2

An exfoliated MoS2 encapsulated into metal-organic frameworks (MOFs) was fabricated as a promising noble-metal-free photocatalyst for hydrogen production under visible light irradiation. The as-synthesized samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) surface analysis. It is well known that bulk MoS2 is unsuitable for photocatalysis due to its inadequate reduction and oxidation capabilities. However, exfoliated MoS2 exhibits a direct band gap of 2.8 eV due to quantum confinement, which enables it to possess suitable band positions and retain a good visible-light absorption ability. As a result, it is considered to be an encouraging candidate for photocatalytic applications. Encapsulating exfoliated MoS2 into MOF demonstrates an improved visible light absorption ability compared to pure MOF, and the highest hydrogen production rate that the encapsulated exfoliated MoS2 could reach was 68.4 μmol h-1g-1, which was much higher than that of pure MOF. With a suitable band structure and improved light-harvesting ability, exfoliated MoS2@MOF could be a potential photocatalyst for hydrogen production.

scholarly journals Synthesis and Characterization of CdS/TiO2-Montmorillonite Nanocomposite with Enhanced Visible-Light Absorption

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Feng-shan Zhou ◽  
Dai-mei Chen ◽  
Bao-lin Cui ◽  
Wei-heng Wang
Keyword(s):  
Visible Light ◽  
Light Absorption ◽  
Photoelectron Spectroscopy ◽  
Synthesis Method ◽  
Cds Nanoparticles ◽  
X Ray Diffraction ◽  
Visible Light Absorption ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Adsorption Desorption

Sodium montmorillonite (MMT) was chosen as the carrier; a serial of CdS/TiO2-MMT nanocomposites with enhanced visible-light absorption ability was prepared by hydrothermal synthesis method combination with semiconductor compound modification method. The samples are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet visible (UV-Vis) spectroscopy; the results showed that TiO2and CdS nanoparticles were loaded on the surface of montmorillonite uniformly. N2adsorption-desorption experiment showed that the specific surface area of TiO2/montmorillonite nanocomposite made by this method can reach 200 m2/g and pore-size distribution was from 4 to 6 nm; UV-Vis showed that the recombination of CdS and TiO2enhanced visible-light absorption ability of samples of TiO2/montmorillonite and visible-light absorption ability increase with the increased of the adsorption of CdS.

Effect of Chromium Doping on Visible Light Absorption of Nanosized Titania Sol-Gel

2009 ◽  
Vol 5 ◽  
pp. 95-104 ◽  
Author(s):  
J.A. Pedraza-Avella ◽  
R. López ◽  
F. Martínez-Ortega ◽  
E.A. Páez-Mozo ◽  
Ricardo Gómez
Keyword(s):  
Visible Light ◽  
Light Absorption ◽  
Photoelectron Spectroscopy ◽  
Diffuse Reflectance Spectroscopy ◽  
Anatase Phase ◽  
Sol Gel ◽  
Visible Light Absorption ◽  
X Ray ◽  
Chromium Doping ◽  
Doped Titania

Visible light absorption of TiO2 can be induced by the addition of transition metal impurities. However, many dissimilar results have been reported about this subject and there are various interpretations about the origin of these absorption features. In this work, samples of chromium-doped titania (TiO2-Cr) with different dopant contents (0.1, 0.5, 1.0 and 5.0 wt. %) were prepared by a sol-gel method. Their particle size was determined by dynamic light scattering and it was on the nanometer scale (18 nm). X-ray powder diffraction and Raman spectroscopy showed only the presence of anatase phase in all samples. X-ray photoelectron spectroscopy reveals that the oxidation state of chromium in the prepared materials is different than in the dopant precursor. This change can be associated to the oxidative gelling conditions used in the materials preparation. UV VIS diffuse reflectance spectroscopy showed that the chromium doping, until 1.0 wt. %, did not effectively narrow the TiO2 band-gap but it induces the visible light absorption probably through the formation of color centers.

Impact of Rutile Fraction on TiO2 Visible-Light Absorption and Visible-Light-Induced Photocatalytic Activity

2018 ◽  
Author(s):  
David Maria Tobaldi ◽  
Luc Lajaunie ◽  
ana caetano ◽  
nejc rozman ◽  
Maria Paula Seabra ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Light Absorption ◽  
Solid Phase ◽  
Diffraction Method ◽  
Band Alignment ◽  
Quantitative Phase Analysis ◽  
Transmission Microscopy ◽  
Visible Light Absorption ◽  
X Ray

<div>Titanium dioxide is by far the most utilised semiconductor material for photocatalytic applications. Still, it is transparent to visible-light. Recently, it has been proved that a type-II band alignment for the rutile−anatase mixture would improve its visible-light absorption.</div><div>In this research paper we thoroughly characterised the real crystalline and amorphous phases of synthesised titanias – thermally treated at different temperatures to get distinct ratios of anatase-rutile-amorphous fraction – as well as that of three commercially available photocatalytic nano-TiO2. </div><div>The structural characterisation was done via advanced X-ray diffraction method, namely the Rietveld-RIR method, to attain a full quantitative phase analysis of the specimens. The microstructure was also investigated via an advanced X-ray method, the whole powder pattern modelling. These methods were validated combining advanced aberration-corrected scanning transmission microscopy and high-resolution electron energy-loss spectroscopy. The photocatalytic activity was assessed in the liquid- and gas-solid phase (employing rhodamine B and 4-chlorophenol, and isopropanol, respectively, as the organic substances to degrade) using a light source irradiating exclusively in the visible-range.</div><div>Optical spectroscopy showed that even a small fraction of rutile (2 wt%) is able to shift to lower energies the apparent optical band gap of an anatase-rutile mixed phase. But is this enough to attain a real photocatalytic activity promoted by merely visible-light?</div><div>We tried to give a reply to that question.</div><div>Photocatalytic activity results in the liquid-solid phase showed that a high surface hydroxylation led to specimen with superior visible light-induced catalytic activity (i.e. dye and ligand-to-metal charge transfer complexes sensitisation effects). That is: not photocatalysis <i>sensu-strictu</i>.</div><div>On the other hand, the gas-solid phase results showed that a higher amount of the rutile fraction (around 10 wt%), together with less recombination of the charge carriers, were more effective for an actual photocatalytic oxidation of isopropanol.</div>

The Photocatalytic Properties of Fe3+ and N Co-Doped TiO2 Micro/Nanofiber Film for Dye Waste Water Decomposition

2011 ◽  
Vol 356-360 ◽  
pp. 853-856 ◽  
Author(s):  
Qiao Zhen Yu ◽  
Xiang Jun Jin ◽  
Shao Yang Li ◽  
Lei Wang ◽  
Kun Long Liang
Keyword(s):  
Waste Water ◽  
Visible Light ◽  
Light Absorption ◽  
Oxygen Demand ◽  
Photocatalytic Efficiency ◽  
Energy Dispersion Spectroscopy ◽  
Visible Light Absorption ◽  
X Ray ◽  
Nano Fiber ◽  
Co Doped

To obtain a TiO2photocatalyst with high photocatalytic efficiency under visible irradiation and good reusability, the Fe3+and N co-doped TiO2micro/nano fiber films were fabricated by electrospinning and calcinations. The morphologies and structures of the resulting samples were analyzed by scanning electron microscopy (SEM), x-ray diffraction and x-ray energy dispersion spectroscopy (EDS). The absorbance and chemical oxygen demand (COD) were characterized respectively by UV–visible spectrophotometer and COD Rapid Tester. The results show that the Fe3+and N co-doped TiO2micro/nano fiber had a multi-porous structure with an average diameter of about 45 to 506 nm. The crystalinity degrees, visible light absorption of these films were affected by the dosage of Fe3+and N co-doping (DFN). Moreover, these films exhibited high photocatalytic activity for the degradation of dye waste water under sunlight and it was related to DFN. As DFN was 0.5 %, it has highest crystalinity degree, largest visible light absorption and highest photocatalytic efficiency on dye waste water. The decolor rate of the dye waste water was as high as 67.6 % and its COD decreased from 2800±200 to 236.40 ± 15.61, when the photocatalytic time was only 3 h.

Extension of the Optical Absorption of TiO2 Nanopaticles to Visible Light Region by Doping with Cobalt

2011 ◽  
Vol 181-182 ◽  
pp. 348-351
Author(s):  
Yi Ding ◽  
Xiao Jun Xu ◽  
Zhang Hua Gan ◽  
Rui Xiong ◽  
Hai Lin Liu
Keyword(s):  
Optical Absorption ◽  
Visible Light ◽  
Light Absorption ◽  
Anatase Phase ◽  
Electron Transition ◽  
Binding Energies ◽  
Visible Absorption ◽  
Visible Light Absorption ◽  
X Ray ◽  
Light Region

TiO2 nanoparticles doped with different cobalt concentrations were fabricated by using so-gel method. The crystal structures and the morphology of the samples were characterized by using x-ray diffractmetry (XRD) and transmission electron microscopy (TEM), respectively. It was found that all the samples are anatase phase and the nanoparticles are of the size around 10 nm. Investigations of the binding energies of different element with X-ray photoelectron spectrometry (XPS) revealed that Co ions are in Co2+ state and take the substitutional sites. No Co clusters were detected in the samples. The optical absorption properties of the samples were studied by using UV-vis absorption spectroscopy. It was noticed that cobalt doped TiO2 has a significant visible light absorption in contrast to pure TiO2: besides a noticeable red shift in absorption edge, an extra visible light absorption peak appears at a wavelength around 600 nm. The visible absorption in cobalt doped TiO2 may attribute to the electron transition from impurity levels induced by the substitutional Co ions and the oxygen vacancies to the conduct band.

scholarly journals Enhanced Visible Light Photocatalytic Activity of Mesoporous AnataseTiO2Codoped with Nitrogen and Chlorine

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Xiuwen Cheng ◽  
Xiujuan Yu ◽  
Zipeng Xing ◽  
Lisha Yang
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Band Gap ◽  
Light Absorption ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Visible Region ◽  
X Ray ◽  
Visible Light Photocatalytic Activity ◽  
Visible Light Photocatalytic

Anatase mesoporous titanium dioxide codoped with nitrogen and chlorine (N-Cl-TiO2) photocatalysts were synthesized through simple one-step sol-gel reactions in the presence of ammonium chloride. The resulting materials were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflection spectrum (UV-vis DRS). XRD results indicated that codoping with nitrogen and chlorine could effectively retard the phase transformation of TiO2from anatase to rutile and the growth of the crystallite sizes. XPS revealed that nitrogen and chlorine elements were incorporated into the lattice of TiO2through substituting the lattice oxygen atoms. DRS exhibited that the light absorption of N-Cl-TiO2in visible region was greatly improved. As a result, the band gap of TiO2was reduced to 2.12 eV. The photocatalytic activity of the as-synthesized TiO2was evaluated for the degradation of RhB and phenol under visible light irradiation. It was found that N-Cl-TiO2catalyst exhibited higher visible light photocatalytic activity than that of P25 TiO2and N-TiO2, which was attributed to the small crystallite size, intense light absorption in visible region, and narrow band gap.

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