Showing papers on "Photocatalysis published in 2010"
TL;DR: It is proposed that TiO (2)-GR cannot provide truly new insights into the fabrication of TiO(2)-carbon composite as high-performance photocatalysts, hence offering a valuable source of reference on fabricating TiO(*(2))-carbon composites for their application as a photocatalyst in the environment cleanup.
Abstract: The nanocomposites of TiO2−graphene (TiO2−GR) have been prepared via a facile hydrothermal reaction of graphene oxide and TiO2 in an ethanol−water solvent. We show that such a TiO2−GR nanocomposite exhibits much higher photocatalytic activity and stability than bare TiO2 toward the gas-phase degradation of benzene, a volatile aromatic pollutant in air. By investigating the effect of different addition ratios of graphene on the photocatalytic activity of TiO2−GR systematically, we find that the higher weight ratio in TiO2−GR will decrease the photocatalytic activity. Analogous phenomenon is also observed for the liquid-phase degradation of dyes over TiO2−GR. In addition, the key features for TiO2−GR including enhancement of adsorptivity of pollutants, light absorption intensity, electron−hole pairs lifetime, and extended light absorption range have also been found in the composite of TiO2 and carbon nanotubes (TiO2−CNT). These strongly manifest that TiO2−GR is in essence the same as other TiO2−carbon (carb...
1,548 citations
TL;DR: The photodegradation mechanisms for two typical dyes, rhodamine B (Rh B) and methyl orange (MO), are proposed based on comparison experiments and the electron paramagnetic resonance was used to detect the active species for the photodegrading reaction over g-C(3)N(4).
Abstract: Graphitic carbon nitride (g-C3N4) and boron-doped g-C3N4 were prepared by heating melamine and the mixture of melamine and boron oxide, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, and UV−vis spectra were used to describe the properties of as-prepared samples. The electron paramagnetic resonance was used to detect the active species for the photodegradation reaction over g-C3N4. The photodegradation mechanisms for two typical dyes, rhodamine B (Rh B) and methyl orange (MO), are proposed based on our comparison experiments. In the g-C3N4 photocatalysis system, the photodegradation of Rh B and MO is attributed to the direct hole oxidation and overall reaction, respectively; however, for the MO photodegradation the reduction process initiated by photogenerated electrons is a major photocatalytic process compared with the oxidation process induced by photogenerated holes. Boron doping for g-C3N4 can promote photodegradation of Rh B because the boron doping improves the dye adsorption and...
1,495 citations
TL;DR: The UV-vis spectra show that the Ti(3+) here extends the photoresponse of TiO(2) from the UV to the visible light region, which leads to high visible-light photocatalytic activity for the generation of hydrogen gas from water.
Abstract: Through a facile one-step combustion method, partially reduced TiO2 has been synthesized. Electron paramagnetic resonance (EPR) spectra confirm the presence of Ti3+ in the bulk of an as-prepared sample. The UV−vis spectra show that the Ti3+ here extends the photoresponse of TiO2 from the UV to the visible light region, which leads to high visible-light photocatalytic activity for the generation of hydrogen gas from water. It is worth noting that the Ti3+ sites in the sample are highly stable in air or water under irradiation and the photocatalyst can be repeatedly used without degradation in the activity.
1,120 citations
TL;DR: In this article, a simple hydrothermal route in a Ti(OC4H9)4-HF-H2O mixed solution followed by a photochemical reduction deposition of Pt nanoparticles on TiO2 nanosheets under xenon lamp irradiation is described.
Abstract: Pt/TiO2 nanosheets with exposed (001) facets were fabricated by a simple hydrothermal route in a Ti(OC4H9)4-HF-H2O mixed solution followed by a photochemical reduction deposition of Pt nanoparticles on TiO2 nanosheets under xenon lamp irradiation. The prepared samples were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption−desorption isotherms, UV−vis diffuse reflectance spectroscopy, and photoluminescence (PL) spectroscopy. Production of •OH radicals on the TiO2 surface was detected by the PL technique using coumarin as a probe molecule. The effects of Pt loading on the rates of photocatalytic hydrogen production of the as-prepared samples in ethanol aqueous solution were investigated and discussed. The results showed that the photocatalytic hydrogen production rates of TiO2 nanosheets from the ethanol aqueous solutions were significantly enhanced by loaded Pt on the TiO2 nanosheets, and the latter with a 2 wt % of deposited Pt exhi...
1,058 citations
TL;DR: A series of titanium dioxide and graphene sheets composites were synthesized with a sol-gel method using tetrabutyl titanate and graphite oxide (GO) as the starting materials.
Abstract: A series of titanium dioxide and graphene sheets (GSs) composites were synthesized with a sol–gel method using tetrabutyl titanate and graphite oxide (GO) as the starting materials. The obtained TiO2/GSs photocatalysts are characterized by X-ray diffraction, N2 adsorption analysis, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared samples was evaluated by hydrogen evolution from water photo-splitting under UV-vis illumination. The influence of GSs content and calcinations atmosphere on the photocatalytic activity was also investigated. The results show that both GSs content and the calcinations atmosphere can affect the photocatalytic activity of the obtained composites.
985 citations
TL;DR: The surface chemistry and the surface structure at the atomic level are key factors in tuning the adsorption selectivity and, consequently, photocatalytic selectivity of HTS toward azo dyes.
Abstract: A fluoride mediated self-transformation method is proposed for the synthesis of hollow TiO2 microspheres (HTS) composed of anatase polyhedra with exposed ca. 20% {001} facets. Importantly, HTS exhibit tunable photocatalytic selectivity in decomposing azo dyes in water. The fluorinated HTS show preferential decomposition of methyl orange (MO) in comparison to methylene blue (MB). In contrast, the surface-modified HTS by either NaOH washing or calcinations at 600 °C favor decomposition of MB over MO. The surface chemistry and the surface structure at the atomic level are key factors in tuning the adsorption selectivity and, consequently, photocatalytic selectivity of HTS toward azo dyes.
982 citations
TL;DR: Mesoporous carbon nitride polymer can function as a metal-free photocatalyst to activate O(2) for the selective oxidation of benzyl alcohols with visible light, avoiding the cost, toxicity, and purification problems associated with corresponding transition-metal systems.
Abstract: Mesoporous carbon nitride (mpg-C3N4) polymer can function as a metal-free photocatalyst to activate O2 for the selective oxidation of benzyl alcohols with visible light, avoiding the cost, toxicity, and purification problems associated with corresponding transition-metal systems. By combining the surface basicity and semiconductor functions of mpg-C3N4, the photocatalytic system can realize a high catalytic selectivity to generate benzaldehyde. The metal-free photocatalytic system also selectively converts other alcohol substrates to their corresponding aldehydes/ketones, demonstrating a potential pathway of accessing traditional mild radical chemistry with nitroxyl radicals.
835 citations
TL;DR: In this paper, a self-assembled GO-TiO 2 nanorod composites (GO and TiO 2 NRCs) can be dispersed in water and the signifi cant increase of photocatalytic activity is confi rmed by the degradation of methylene blue (MB) under UV light irridiation.
Abstract: TiO 2 nanorods are self-assembled on the graphene oxide (GO) sheets at the water/toluene interface. The self-assembled GO–TiO 2 nanorod composites (GO–TiO 2 NRCs) can be dispersed in water. The effective anchoring of TiO 2 nanorods on the whole GO sheets is confi rmed by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), and thermogravimetric analysis (TGA). The signifi cant increase of photocatalytic activity is confi rmed by the degradation of methylene blue (MB) under UV light irridiation. The large enhancement of photocatalytic activity is caused by the effective charge anti-recombination and the effective absorption of MB on GO. The effective charge transfer from TiO 2 to GO sheets is confi rmed by the signifi cant photoluminescence quenching of TiO 2 nanorods, which can effectively prevent the charge recombination during photocatalytic process. The effective absorption of MB on GO is confi rmed by the UV-vis spectra. The degradation rate of MB in the second cycle is faster than that in the fi rst cycle because of the reduction of GO under UV light irradiation.
725 citations
TL;DR: In this paper, a modified Hummers' procedure was used to synthesize a graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4-4.3
Abstract: A graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4–4.3 eV is synthesized by a modified Hummers' procedure. The as-synthesized GO photocatalyst has an interlayer spacing of 0.42 nm because of its moderate oxidation level. Under irradiation with UV or visible light, this GO photocatalyst steadily catalyzes H2 generation from a 20 vol % aqueous methanol solution and pure water. As the GO sheets extensively disperse in water, a cocatalyst is not required for H2 generation over the GO photocatalyst. During photocatalytic reaction, the GO loses some oxygen functional groups, leading to bandgap reduction and increased conductivity. This structural variation does not affect the stable H2 generation over the GO. The encouraging results presented in this study demonstrate the potential of graphitic materials as a medium for water splitting under solar illumination.
719 citations
TL;DR: In this article, the effects of various operating parameters on the photocatalytic degradation of phenols and substituted phenols are presented, such as type of photocatalyst and composition, light intensity, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, oxidising agents/electron acceptors, mode of catalyst application, and calcination temperatures.
705 citations
TL;DR: In this paper, a graphene/TiO2 nanocrystals hybrid has been successfully prepared by directly growing TiO2 nanopocrystals on graphene oxide (GO) sheets by a two-step method.
Abstract: A graphene/TiO2 nanocrystals hybrid has been successfully prepared by directly growing TiO2 nanocrystals on graphene oxide (GO) sheets. The direct growth of the nanocrystals on GO sheets was achieved by a two-step method, in which TiO2 was first coated on GO sheets by hydrolysis and crystallized into anatase nanocrystals by hydrothermal treatment in the second step. Slow hydrolysis induced by the use of EtOH/H2O mixed solvent and addition of H2SO4 facilitates the selective growth of TiO2 on GO and suppresses growth of free TiO2 in solution. The method offers easy access to the GO/TiO2 nanocrystals hybrid with a uniform coating and strong interactions between TiO2 and the underlying GO sheets. The strong coupling gives advanced hybrid materials with various applications including photocatalysis. The prepared graphene/TiO2 nanocrystals hybrid has superior photocatalytic activity to other TiO2 materials in the degradation of rhodamine B, showing an impressive three-fold photocatalytic enhancement over P25. It is expected that the hybrid material could also be promising for various other applications including lithium ion batteries, where strong electrical coupling to TiO2 nanoparticles is essential.
TL;DR: The results suggest that the photocatalysis efficiency of nanocrystals can be significantly improved by tailoring the shape and the surface structure of nanocystals, which provides a new concept for rational design and development of high-performance photocatalysts.
Abstract: Particle size is generally considered to be the primary factor in the design of nanocrystal photocatalysts, because the reduction of particle size increases the number of active sites. However, the benefit from the size reduction can be canceled by a higher electron-hole recombination rate due to the confined space in sphere-shaped nanoparticles. Here we report a mechanistic study on a novel nanobelt structure that overcomes the drawback of sphere-shaped nanoparticles. Single-crystalline anatase TiO(2) nanobelts with two dominant surfaces of (101) facet exhibit enhanced photocatalytic activity over the nanosphere counterparts with an identical crystal phase and similar specific surface area. The ab initio density functional theory (DFT) calculations show that the exposed (101) facet of the nanobelts yields an enhanced reactivity with molecular O(2), facilitating the generation of superoxide radical. Moreover, the nanobelts exhibit a lower electron-hole recombination rate than the nanospheres due to the following three reasons: (i) greater charge mobility in the nanobelts, which is enabled along the longitudinal dimension of the crystals; (ii) fewer localized states near the band edges and in the bandgap due to fewer unpassivated surface states in the nanobelts; and (iii) enhanced charge separation due to trapping of photogenerated electrons by chemisorbed molecular O(2) on the (101) facet. Our results suggest that the photocatalysis efficiency of nanocrystals can be significantly improved by tailoring the shape and the surface structure of nanocrystals, which provides a new concept for rational design and development of high-performance photocatalysts.
TL;DR: Pt/WO3 photocatalyst that oxidizes various substrates under visible light with a sufficient photostability can be applied for solar water treatment.
Abstract: This study aims to understand the visible light photocatalytic activities of platinized WO3 (Pt/WO3) on the degradation of aquatic pollutants and the role of main photooxidants. The presence of Pt on WO3 is known to facilitate the multielectron reduction of O2, which enables O2 to serve as an electron acceptor despite the insufficient reduction potential of the conduction band electrons (in WO3) for the one-electron reduction of O2. The concurrent oxidative reactions occurring on WO3 were markedly enhanced in the presence of Pt and accompanied the production of OH radicals under visible light, which was confirmed by both a fluorescence method (using a chemical trap) and a spin trap method. The generation of OH radicals mainly comes from the reductive decomposition of H2O2 that is produced in situ from the reduction of O2 on Pt/WO3. The rate of in situ production of H2O2 under visible light was significantly faster with Pt/WO3 than WO3. Six substrates that were tested for the visible light (λ > 420 nm) ind...
TL;DR: In this article, a series of N-doped anatase TiO2 samples have been prepared using a solvothermal method in an organic amine/ethanol-water reaction system, and the effects of different starting N : Ti atomic ratios on the catalysts structure, surface property and catalytic activity have been investigated.
Abstract: A series of N-doped anatase TiO2 samples have been prepared using a solvothermal method in an organic amine/ethanol–water reaction system. The effects of different starting N : Ti atomic ratios on the catalysts structure, surface property and catalytic activity have been investigated. The photocatalytic activity and stability of the N-doped TiO2 samples were evaluated through using the decomposition of Methylene blue (MB) and Methyl orange (MO) as model reaction under visible light irradiation. Characterization results show that the nitrogen dopant has a significant effect on the crystallite size and optical absorption of TiO2. It was found that the N-doped TiO2 catalysts have enhanced absorption in the visible light region, and exhibit higher activity for photocatalytic degradation of model dyes (e.g. MB and MO). The catalyst with the highest performance was the one prepared using N : Ti molar ratio of 1.0. Electron paramagnetic resonance (EPR) measurement suggests the materials contain Ti 3+ ions, with both the degree of N doping and oxygen vacancies make contributions to the visible light absorption of TON. The presence of superoxide radicals (O u � ) and hydroxyl radicals (OH) on the surface of TON were found to be responsible for MB and MO solution decoloration under visible light. Based on the results of the present study, a visible light induced photocatalytic mechanism has been proposed for N-doped anatase TiO2.
TL;DR: In this paper, the authors discuss the interpretation of what we know and what we do not know in a scientific sense, in alphabetical order from activity, band structure, and crystallinity to X-ray photoelectron spectroscopy.
Abstract: Topics, in alphabetical order from “Activity”, “Band structure” and “Crystallinity” to “X-ray photoelectron spectroscopy”, “Yield” and “Z-scheme photocatalysis”, related to photocatalysis and photoelectrochemical reaction are discussed with interpretation of what we know and what we do not know in a scientific sense.
TL;DR: In this paper, the photocatalytic degradation of organic dyes containing different functionalities using TiO2 nanomaterials in aqueous solution is discussed and the influence of different substitutes such as alkyl side chains, methyl, nitrate, hydroxyl and carboxylic groups as well as the presence of chloro atom have been discussed in detail.
Abstract: Synthetic dyes are a major part of our life as they are found in the various products ranging from clothes to leather accessories to furniture. These carcinogenic compounds are the major constituents of the industrial effluents. Various approaches have been developed to remove organic dyes from the natural environment. Over the past few years, there has been an enormous amount of research with advanced oxidation processes (AOPs) as an effective method of wastewater treatment. Among AOPs, heterogeneous photocatalytic process using TiO2 nanomaterials appears as the most emerging destructive technology due to its cost effectiveness and the catalyst inert nature and photostability. This review deals with the photocatalytic degradation of organic dyes containing different functionalities using TiO2 nanomaterials in aqueous solution. It first discusses the photocatalytic properties of nanostructured TiO2. The photocatalytic degradation rate strongly depends on the basic structure of the molecule and the nature of auxiliary groups attached to the aromatic nuclei of the dyes. So, this review then explains the influence of structure of dyes on their photocatalytic degradation rates. The influences of different substitutes such as alkyl side chains, methyl, nitrate, hydroxyl and carboxylic groups as well as the presence of chloro atom have been discussed in detail.
TL;DR: This work provides a potential effective VLD photocatalyst to disinfect the bacterial cells, even to destruct the biofilm that can provide shelter and substratum for microorganisms and resist to disinfection.
Abstract: Urgent development of effective and low-cost disinfecting technologies is needed to address the problems caused by an outbreak of harmful microorganisms. In this work, we report an effective photocatalytic disinfection of E. coli K-12 by using a AgBr-Ag-Bi(2)WO(6) nanojunction system as a catalyst under visible light (lambda >or= 400 nm) irradiation. The visible-light-driven (VLD) AgBr-Ag-Bi(2)WO(6) nanojunction could completely inactivate 5 x 10(7) cfu mL(-1) E. coli K-12 within 15 min, which was superior to other VLD photocatalysts such as Bi(2)WO(6) superstructure, Ag-Bi(2)WO(6) and AgBr-Ag-TiO(2) composite. Moreover, the photochemical mechanism of bactericidal action for the AgBr-Ag-Bi(2)WO(6) nanojunction was investigated by using different scavengers. It was found that the diffusing hydroxyl radicals generated both by the oxidative pathway and the reductive pathway play an important role in the photocatalytic disinfection. Moreover, direct contact between the AgBr-Ag-Bi(2)WO(6) nanojunction and bacterial cells was not necessary for the photocatalytic disinfection of E. coli K-12. Finally, the photocatalytic destruction of the bacterial cells was directly observed by TEM images and further confirmed by the determination of potassium ion (K(+)) leakage from the killed bacteria. This work provides a potential effective VLD photocatalyst to disinfect the bacterial cells, even to destruct the biofilm that can provide shelter and substratum for microorganisms and resist to disinfection.
TL;DR: A high photocatalytic BiPO(4) with a novel nonmetal oxy acid structure is synthesized by a hydrothermal method and the inductive effect of PO(4)(3-) helps the e(-)/h(+) separation, which plays an important role in its excellent photoc atalytic activity.
Abstract: A high photocatalytic BiPO4 with a novel nonmetal oxy acid structure is synthesized by a hydrothermal method. BiPO4 photocatalyst has an optical indirect band gap of 3.85 eV. In a comparison of BiPO4 with that of TiO2 (P25, Degussa), it is found that the photocatalytic activity of BiPO4 is twice that of TiO2 (P25, Degussa) for the degradation of methylene blue (MB) dye, while the BET surface of BiPO4 is just one tenth of that of P25. Both the high position of the valence band and the high separation efficiency of electron−hole pairs result in the high photocatalytic activity. The inductive effect of PO43− helps the e−/h+ separation, which plays an important role in its excellent photocatalytic activity. It may extend to the synthesis of other inorganic nonmetal salts of oxy photocatalysts with suitable band gap and high activity for the environmental purification of organic pollutants in aqueous solution.
TL;DR: The obviously increased performance of g-C(3)N(4)-TaON is ascribed mainly to enhancement of electron-hole separations both at the interface and in the semiconductors.
Abstract: Organic–inorganic composite photocatalyst g-C3N4–TaON with visible-light response was prepared by a milling-heat treatment method. The photocatalyst was characterized by X-ray diffraction, high-resolution transmission electron microscopy and UV-vis diffuse reflection spectroscopy. The activity of composite photocatalyst g-C3N4–TaON for photodegradation of rhodamine B is higher than that of either single-phase g-C3N4 or TaON. The obviously increased performance of g-C3N4–TaON is ascribed mainly to enhancement of electron–hole separations both at the interface and in the semiconductors.
TL;DR: Based on the XRD and XPS patterns of the AgI/BiOI composites before and after reaction, AgI was stable in the composites under visible irradiation, indicating that AgI /BiOi composites could be used as stable and efficient visible-light-induced photocatalysts.
Abstract: The nanostructured AgI/BiOI composites were prepared by a facile, one-step, and low temperature chemical bath method with Bi(NO(3))(3), AgNO(3), and KI. Several characterization tools, such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), the Brunauer-Emmett-Teller (BET) surface area, photoluminescence (PL) spectra, and UV-vis diffuse reflectance spectroscopy, were employed to study the phase structures, morphologies, and optical properties of the samples. The PL intensity of AgI was greatly decreased when combined with BiOI, indicating the corresponding decreased recombination of the carriers. The photocatalytic properties of the as-prepared products were measured with the degradation of methyl orange and phenol at room temperature under visible light irradiation. The AgI/BiOI composites showed much higher photocatalytic performances over BiOI as well as AgI. It was also found that the AgI amount in the AgI/BiOI composites played an important role in the corresponding photocatalytic properties and the optimized ratio was obtained at 20%. The dramatic enhancement in the visible light photocatalytic performance of the AgI/BiOI composites could be attributed to the effective electron-hole separations at the interfaces of the two semiconductors, which facilitate the transfer of the photoinduced carriers. By the detection of hydroxyl radicals through a fluorescence technique, the photoinduced holes (h(VB)(+)) were considered to be the dominant active species in the photodegradation process, which was also deduced from the theoretical speculations. The photocatalytic performances of the AgI/BiOI composites were maintained for the cycling experiments. In addition, based on the XRD and XPS patterns of the AgI/BiOI composites before and after reaction, AgI was stable in the composites under visible irradiation, indicating that AgI/BiOI composites could be used as stable and efficient visible-light-induced photocatalysts.
TL;DR: In this paper, a carbon nanotubes (CNT)/TiO2 nanocomposite photocatalyst has been prepared by a simple impregnation method, which is used, for the first time, for gas-phase degradation of benzene.
Abstract: A carbon nanotubes (CNT)/TiO2 nanocomposite photocatalyst has been prepared by a simple impregnation method, which is used, for the first time, for gas-phase degradation of benzene. It is found that the as-prepared CNT/TiO2 nanocomposite exhibits an enhanced photocatalytic activity for benzene degradation, as compared with that over commerical titania (Degussa P25). A similar phenomenon has also been found for liquid-phase degradation of methyl orange. The characterization of photocatalysts by a series of joint techniques, including X-ray diffraction, transmission electron microscopy, ultraviolet/visible (UV/vis) diffuse reflectance spectra, and photoluminescence spectra, discloses that CNT has two kinds of crucial roles in enhancement of photocatalytic activity of TiO2. One is to act as an electron reservoir, which helps to trap electrons emitted from TiO2 particles due to irradiation by UV light, therefore hindering electron−hole pairs recombination. The other is to act as a dispersing template or suppo...
TL;DR: A plasmonic photocatalyst supported on mesoporous alumina (Ag−AgI/Al2O3) was prepared by deposition−precipitation and photoreduction methods as mentioned in this paper.
Abstract: A plasmonic photocatalyst Ag−AgI supported on mesoporous alumina (Ag−AgI/Al2O3) was prepared by deposition−precipitation and photoreduction methods. The catalyst showed high and stable photocatalytic activity for the degradation and mineralization of toxic persistent organic pollutants, as demonstrated with 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), and trichlorophenol (TCP) under visible light or simulated solar light irradiation. On the basis of electron spin resonance, cyclic voltammetry analyses under a variety of experimental conditions, two electron transfer processes were verified from the excited Ag NPs to AgI and from 2-CP to the Ag NPs, and the main active species of O2•− and excited h+ on Ag NPs were involved in the photoreaction system of Ag−AgI/Al2O3. A plasmon-induced photocatalytic mechanism was proposed. Accordingly, the plasmon-induced electron transfer processes elucidated the photostability of Ag−AgI/Al2O3. This finding indicates that the high photosensitivity of noble metal N...
TL;DR: Graphene modified with gold nanoparticles displayed an excellent visible-light photocatalytic performance in degrading dyes in water.
TL;DR: Large rutile particles loaded with gold particles of a wide range of sizes showed the highest level of photocatalytic activity, possibly due to greater light absorption ability in a wide wavelength range resulting from transverse and longitudinal LSPR of rod-like gold particles.
Abstract: Fifteen commercial titania (titanium(IV) oxide; TiO2) powders were modified with gold by photodeposition to prepare photocatalysts that work under irradiation with light in the visible range (vis). The gold-modified titania (Au/TiO2) powders were characterized by diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), scanning transmission microscopy (STEM) and X-ray powder diffraction (XRD). It was shown that all tested powders could absorb visible light with an absorption maximum at localized surface plasmon resonance (LSPR) wavelengths (530–600 nm) and that the size and shape of gold nanoparticles determined the absorption ranges. The photocatalytic activity of Au/TiO2 powders was examined both under ultraviolet and vis irradiation (mainly >450 nm) for acetic acid and 2-propanol photooxidation. It was found that the activity depended strongly on gold and titania properties, such as particle size and shape, surface area and crystalline form. Under vis irradiation, large rutile particles loaded with gold particles of a wide range of sizes showed the highest level of photocatalytic activity, possibly due to greater light absorption ability in a wide wavelength range resulting from transverse and longitudinal LSPR of rod-like gold particles. Action spectrum analyses showed that visible-light-induced oxidation of organic compounds by aerated gold–titania suspensions was initiated by excitation of LSPR absorption of gold. Although photocatalytic activity of nanosized gold particles under vis irradiation with a wavelength of ca. 430 nm and catalytic activity of gold-modified titania during dark reactions were also found, it was shown that the activities of Au/TiO2 particles originated from activation of LSPR of gold by light of wavelength of 530–650 nm. Participation of molecular oxygen as an electron acceptor and titania as a conductor of electrons is suggested by comparing with results obtained under deaerated conditions and results obtained using a system containing gold-deposited silica instead of gold–titania, respectively. On the basis of these results, the mechanism of visible-light-induced oxidation of organic compounds on gold–titania is proposed.
TL;DR: Fluorination of polymeric carbon nitride solids has been performed by using ammonium fluoride as a cheap fluorine source as mentioned in this paper, which not only provides the modified open texture but also enables the effective adjustment of the electronic band gaps, which makes them exhibit excellent photocatalytic activity in both hydrogen production from water and oxidization of benzene to phenol under visible light.
Abstract: Fluorination of polymeric carbon nitride solids has been performed by using ammonium fluoride as a cheap fluorine source. It is clear that fluorination not only provides the modified open texture but also enables the effective adjustment of the electronic band gaps, which makes them exhibit excellent photocatalytic activity in both hydrogen production from water and oxidization of benzene to phenol under visible light.
TL;DR: A critical review on the advancements in sol-gel method of doping TiO2 photocatalysts is provided in this paper, where various solgel and related systems of doping were considered, ranging from co-doping, transition metal ions doping, rare earth metal ion doping to other metals and non-metals ions doping of TiO 2.
Abstract: A critical review on the advancements in sol–gel method of doping TiO2 photocatalysts is provided Various sol–gel and related systems of doping were considered, ranging from co-doping, transition metal ions doping, rare earth metal ions doping to other metals and non-metals ions doping of TiO2 The results available showed that doping TiO2 with transition metal ions usually resulted in a hampered efficiency of the TiO2 photocatalyst, though in some few cases, enhancements of the photocatalytic activity of TiO2 were recorded by doping it with some transition metal ions In most cases, co-doping of TiO2 increases the efficiency of its photocatalytic activity The review reveals that there are some elemental ions that cannot be used to dope TiO2 because of their negative effects on the photocatalytic activity of the catalyst, while others must be used with caution as their doping will create minimal or no impacts on the TiO2 photocatalytic efficiency
TL;DR: Well-defined m-BiVO(4) nanoplates with exposed {001} facets have been synthesized by a facile hydrothermal route, without the use of any template or organic surfactant, and exhibit greatly enhanced activity in the visible-light photocatalytic degradation of organic contaminants and photocatalyst oxidation of water for O(2) generation.
TL;DR: In this article, surface-fluorinated anatase TiO 2 nanosheets with dominant {0,0,1} facets were fabricated by a simple hydrothermal route in a Ti(OC 4 H 9 ) 4 -HF-H 2 O mixed solution.
Abstract: Surface-fluorinated anatase TiO 2 nanosheets with dominant {0 0 1} facets were fabricated by a simple hydrothermal route in a Ti(OC 4 H 9 ) 4 -HF-H 2 O mixed solution. The atomic ratios of fluorine to titanium ( R F ) exhibit an obvious influence on the structures and photocatalytic activity of TiO 2 samples. In the presence of HF, TiO 2 nanosheets can be easily obtained. With increasing R F , the relative anatase crystallinity, average crystallite size, pore size and percentage of exposed {0 0 1} facets increase, contrarily, BET specific surface areas decrease. All fluorinated TiO 2 nanosheets exhibit much higher photocatalytic activity than Degussa P-25 TiO 2 (P25) and pure TiO 2 nanoparticles prepared in pure water due to the synergistic effect of surface fluorination and exposed {0 0 1} facets on the photoactivity of TiO 2 . Especially, at R F = 1, the fluorinated TiO 2 nanosheet exhibits the highest photocatalytic activity, and its photoactivity exceeds that of P25 by a factor of more than nine times.
TL;DR: In this paper, a multifunctional Au-coated TiO 2 nanotube array is made via synthesis of a ZnO template, followed by deposition of Au particles onto the surface using photocatalytic deposition and a hydrothermal method, respectively.
Abstract: A multifunctional Au-coated TiO 2 nanotube array is made via synthesis of a TiO 2 nanotube array through a ZnO template, followed by deposition of Au particles onto the TiO 2 surface using photocatalytic deposition and a hydrothermal method, respectively. Such arrays exhibit superior detection sensitivity with high reproducibility and stability. In addition, due to possessing stable catalytic properties, the arrays can clean themselves by photocatalytic degradation of target molecules adsorbed to the substrate under irradiation with UV light into inorganic small molecules using surface-enhanced Raman spectroscopy (SERS) detection, so that recycling can be achieved. Finally, by detection of Rhodamine 6G (R6G) dye, herbicide 4-chlorophenol (4-CP), persistent organic pollutant (POP) dichlorophenoxyacetic acid (2,4-D), and organophosphate pesticide methyl-parathion (MP), the unique recyclable properties indicate a new route in eliminating the single-use problem of traditional SERS substrates and show promising applications for detecting other organic pollutants.
TL;DR: In this paper, the rate constants for the reaction of ciprofloxacin with several free radicals, OH, N 3 and SO 4 − as well as hydrated electrons were reported.
Abstract: Fluoroquinolones and their metabolites are found in surface and ground waters, indicating their ineffective removal by conventional water treatment technologies. Advanced oxidation processes (AOPs) are alternatives to traditional water treatments. They utilize free radical reactions to directly degrade fluoroquinolones. This work reports absolute rate constants for the reaction of ciprofloxacin with several free radicals, OH, N 3 and SO 4 − as well as hydrated electrons. Pulsed radiolysis experiments showed that OH, N 3 and e aq − reacted quickly with ciprofloxacin, with bimolecular reaction rate constants of (2.15 ± 0.10) × 10 10 , (2.90 ± 0.12) × 10 10 and (2.65 ± 0.15) × 10 10 M −1 s −1 , respectively, while the SO 4 − radical appeared not to react with ciprofloxacin. Transient spectra were observed for the intermediate radicals produced by hydroxyl and azide radical reactions. Moreover, ciprofloxacin can be degraded rapidly using a typical advanced oxidation process, TiO 2 photocatalysis, with half-lives of 1.9–10.9 min depending upon pH values. Seven degradation products were elucidated by LC/MS/MS analysis, and the degradation mechanism of ciprofloxacin was also tentatively proposed by combining the experimental evidence with theoretical calculations of frontier electron densities. The calculations suggest that the addition of a hydroxyl radical to ciprofloxacin and photo-hole direct attack is two predominant reaction pathways.