Low temperature preparation and visible light photocatalytic activity of mesoporous carbon-doped crystalline TiO2
TL;DR: In this paper, a carbon-doped TiO2 photocatalyst was obtained by using glucose as a carbon source and was characterized by XRD, XPS, TEM, nitrogen adsorption, and UV-vis diffuse reflectance spectroscopy.
Abstract: A visible-light-active TiO2 photocatalyst was prepared through carbon doping by using glucose as carbon source. Different from the previous carbon-doped TiO2 prepared at high temperature, our preparation was performed by a hydrothermal method at temperature as low as 160 °C. The resulting photocatalyst was characterized by XRD, XPS, TEM, nitrogen adsorption, and UV–vis diffuse reflectance spectroscopy. The characterizations found that the photocatalyst possessed a homogeneous pore diameter about 8 nm and a high surface area of 126 m2/g. Comparing to undoped TiO2, the carbon-doped TiO2 showed obvious absorption in the 400–450 nm range with a red shift in the band gap transition. It was found that the resulting carbon-doped TiO2 exhibits significantly higher photocatalytic activity than the undoped counterpart and Degussa P25 on the degradation of rhodamine B (RhB) in water under visible light irradiation (λ > 420 nm). This method can be easily scaled up for industrial production of visible-light driven photocatalyst for pollutants removal because of its convenience and energy-saving.
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TL;DR: A chemically bonded TiO(2) (P25)-graphene nanocomposite photocatalyst with graphene oxide and P25, using a facile one-step hydrothermal method could provide new insights into the fabrication of a TiO (2)-carbon composite as high performance photocatalysts and facilitate their application in the environmental protection issues.
Abstract: Herein we obtained a chemically bonded TiO2 (P25)-graphene nanocomposite photocatalyst with graphene oxide and P25, using a facile one-step hydrothermal method. During the hydrothermal reaction, both of the reduction of graphene oxide and loading of P25 were achieved. The as-prepared P25-graphene photocatalyst possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously, which was rarely reported in other TiO2−carbon photocatalysts. Hence, in the photodegradation of methylene blue, a significant enhancement in the reaction rate was observed with P25-graphene, compared to the bare P25 and P25-CNTs with the same carbon content. Overall, this work could provide new insights into the fabrication of a TiO2−carbon composite as high performance photocatalysts and facilitate their application in the environmental protection issues.
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TL;DR: The field of surface science provides a unique approach to understand bulk, surface and interfacial phenomena occurring during TiO2 photocatalysis as mentioned in this paper, including photon absorption, charge transport and trapping, electron transfer dynamics, adsorbed state, mechanisms, poisons and promoters, and phase and form.
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TL;DR: In this paper, the authors summarized recent research dealing with development of titanium dioxide (TiO2) used for environmental applications and suggested new research directions, including preparation aspects for the development of this promising material.
Abstract: This paper summarizes recent research dealing with development of titanium dioxide (TiO2) used for environmental applications. TiO2 plays the most important role owing to its excellent chemical and physical properties. However, the TiO2 band edge lies in the UV region that makes them inactive under visible irradiation. In this regard, considerable efforts have been made to increase the visible light activity of TiO2 via the modification of its electronic and optical properties. Doping TiO2 using either anions or cations is one of the typical approaches that has been largely applied. Coupling TiO2 with a narrow bad gap semiconductor (MxOy/TiO2 or MxSy/TiO2) represents another approach. This work aims to encompass the new progress of TiO2 for an efficient application in water and wastewater treatment under visible light, emphasizes the future trends of TiO2 in the environment, and suggests new research directions, including preparation aspects for the development of this promising material.
1,281 citations
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TL;DR: In this paper, a general one-pot solvothermal process was explored to prepare BiOX (X = Cl, Br, I) powders by employing ethylene glycol as the solvent.
Abstract: A general one-pot solvothermal process was explored to prepare BiOX (X = Cl, Br, I) powders by employing ethylene glycol as the solvent. The as-prepared BiOX powders were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, UV−vis diffuse reflectance spectroscopy, and nitrogen sorption. The resulting BiOX samples were phase-pure and of hierarchical microspheres consisting of nanoplates. The band gaps of the as-prepared powders were estimated to about 3.22, 2.64, and 1.77 eV for BiOCl, BiOBr, and BiOI, respectively. On the basis of characterization results, we proposed a possible process for the growth of hierarchical BiOX nanoplate microspheres. Moreover, we evaluated their photocatalytic activities on the degradation of methyl orange and compared them with TiO2 (Degussa, P25) under UV−vis light irradiation and C-doped TiO2 under visible light (λ > 420 nm) irradiation, respectively. It was found that al...
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TL;DR: In this paper, a review of the literature on nanocarbon-TiO2 photocatalysts is presented, highlighting recent progress in the development of carbon dioxide photocatalyst.
1,075 citations
References
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TL;DR: Mise au point comportant des definitions generales et la terminologie, la methodologie utilisee, les procedes experimentaux, les interpretations des donnees d'adsorption, les determinations de l'aire superficielle, and les donnes sur la mesoporosite et la microporosite.
Abstract: Mise au point comportant des definitions generales et la terminologie, la methodologie utilisee, les procedes experimentaux, les interpretations des donnees d'adsorption, les determinations de l'aire superficielle, et les donnees sur la mesoporosite et la microporosite
20,347 citations
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TL;DR: Film and powders of TiO2-x Nx have revealed an improvement over titanium dioxide (TiO2) under visible light in optical absorption and photocatalytic activity such as photodegradations of methylene blue and gaseous acetaldehyde and hydrophilicity of the film surface.
Abstract: To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Films and powders of TiO 2- x N x have revealed an improvement over titanium dioxide (TiO 2 ) under visible light (wavelength 2 has proven to be indispensable for band-gap narrowing and photocatalytic activity, as assessed by first-principles calculations and x-ray photoemission spectroscopy.
11,402 citations
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TL;DR: A chemically modified n-type TiO2 is synthesized by controlled combustion of Ti metal in a natural gas flame and performs water splitting with a total conversion efficiency of 11% and a maximum photoconversion efficiency of 8.35% when illuminated at 40 milliwatts per square centimeter.
Abstract: Although n-type titanium dioxide (TiO2) is a promising substrate for photogeneration of hydrogen from water, most attempts at doping this material so that it absorbs light in the visible region of the solar spectrum have met with limited success. We synthesized a chemically modified n-type TiO2 by controlled combustion of Ti metal in a natural gas flame. This material, in which carbon substitutes for some of the lattice oxygen atoms, absorbs light at wavelengths below 535 nanometers and has a lower band-gap energy than rutile (2.32 versus 3.00 electron volts). At an applied potential of 0.3 volt, chemically modified n-type TiO2 performs water splitting with a total conversion efficiency of 11% and a maximum photoconversion efficiency of 8.35% when illuminated at 40 milliwatts per square centimeter. The latter value compares favorably with a maximum photoconversion efficiency of 1% for n-type TiO2 biased at 0.6 volt.
3,911 citations
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TL;DR: In this article, the presence of metal ion dopants in the TiO_2 crystalline matrix significantly influences photoreactivity, charge carrier recombination rates, and interfacial electron-transfer rates.
Abstract: A systematic study of metal ion doping in quantum (Q)-sized (2-4 nm) TiO_2 colloids is performed by measuring their photoreactivities and the transient charge carrier recombination dynamics. The presence of metal ion dopants in the TiO_2 crystalline matrix significantly influences photoreactivity, charge carrier recombination rates, and interfacial electron-transfer rates. The photoreactivities of 21 metal ion-doped colloids are quantified in terms of both the conduction band electron reduction of an electron acceptor (CCl_4 dechlorination) and the valence band hole oxidation of an electron donor (CHCl_3 degradation). Doping with Fe^(3+), Mo^(5+), Ru^(3+), Os^(3+), Re^(5+), V^(4+), and Rh^(3+) at 0.1-0.5 at.% significantly increases the photoreactivity for both oxidation and reduction while Co^(3+) and Al^(3+) doping decreases the photoreactivity. The transient absorption signals upon laser flash photolysis (λ_(ex) = 355 nm) at λ = 600 nm are extended up to 50 ms for Fe^(3+)-, V^(4+)-, Mo^(5+)-, and Ru^(3+)-doped TiO_2 while the undoped Q-sized TiO_2 shows a complete "blue electron" signal decay within 200 μs. Co^(3+)- and Al^(3+)-doped TiO_2 are characterized by rapid signal decays with a complete loss of absorption signals within 5 μs. The quantum yields obtained during CW photolyses are quantitatively correlated with the measured transient absorption signals of the charge carriers. Photoreactivities
are shown to increase with the relative concentration of trapped charge carriers. The photoreactivity of doped TiO_2 appears to be a complex function of the dopant concentration, the energy level of dopants within the TiO_2 lattice, their d electronic configuration, the distribution of dopants, the electron donor concentration, and the light intensity.
3,508 citations
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TL;DR: Only amorphous silica and some colloidal polymer spheres can be routinely prepared with satisfactorily narrow size distributions, and surface modification almost unavoidable before use as supports or templates.
Abstract: Colloidal microand nanospheres have been of continuous research interest, since their intrinsic properties can be finely tuned by changing parameters such as diameter, chemical composition, bulk structure, and crystallinity. Up to now, they have found a broad range of applications in fields such as drug delivery, biodiagnostics, combinatorial synthesis, and photonic band-gap crystals (PBG). The success of these applications strongly depends on the availability of colloidal spheres with tightly controlled size and surface properties. However, until now, only amorphous silica and some colloidal polymer spheres can be routinely prepared with satisfactorily narrow size distributions. As-prepared colloidal nanoand microspheres usually have relatively inert surfaces, which make surface modification almost unavoidable before use as supports or templates.
2,102 citations