Photocatalytic activity of polymer-modified ZnO under visible light irradiation

Photocatalytic removal of phenol, rhodamine B, and methyl orange was studied using the photocatalyst ZnO/poly-(fluorene-co-thiophene) (PFT) under visible light. After 2 h irradiation with three 1 W LED (light-emitting diode) lights, about 40% removal of both phenol and methyl orange was achieved; rhodamine B was completely degraded to rhodamine. Diffuse reflectance spectra showed that the absorbance range of PFT/ZnO was expanded from 387 nm (ZnO) to about 500 nm. Photoluminescent spectra and photoluminescent quantum efficiency indicated that electrons were transferred from PFT to the conduction band of ZnO. Electron spin resonance (ESR) signals of spin-trapped paramagnetic species with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) evidenced that the OH* radicals were indeed formed in the PFT/ZnO system under visible light irradiation. A working mechanism involving excitation of PFT, followed by charge injection into the ZnO conduction band is proposed.     

Synthesis and photochemical performance of CdS nanoparticles photocatalysts for photodegradation of organic dye

Large scale CdS nanoparticles are synthesized by a facile and effective route. The as-prepared CdS product was characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electronmicroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectroscopy. The CdS nanoparticles showed higher photocatalytic activity for the discoloration of methyl orange under UV light irradiation for 90 min. Significantly, the stability and recycling of the photocatalyst was also investigated. This study may provide a new insight into the design and prepared of visible-light photocatalytic materials.     

Photocatalytic performance of Gd ion modified titania porous hollow spheres under visible light

In this work, Gd-doped titania hollow spheres were prepared using hydrothermally prepared carbon spheres as template. The prepared samples were characterized by XRD, TEM, SEM, DRS and XPS. The photocatalytic activity of as-prepared hollow titania spheres was determined by degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under visible light irradiation. The effect of Gd content on the physical structure and photocatalytic properties of doped titania hollow sphere samples was investigated. Results showed that there was an optimal Gd-doped content (4%) for the photocatalytic activity of X-3B degradation.     

Photocatalytic degradation of Orange G on nitrogen-doped TiO2 catalysts under visible light and sunlight irradiation

In this paper, the degradation of an azo dye Orange G (OG) on nitrogen-doped TiO₂ photocatalysts has been investigated under visible light and sunlight irradiation. Under visible light irradiation, the doped TiO₂ nanocatalysts demonstrated higher activity than the commercial Dugussa P25 TiO₂, allowing more efficient utilization of solar light, while under sunlight, P25 showed higher photocatalytic activity. According to the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis spectra analyses, it was found that both the nanosized anatase structure and the appearance of new absorption band in the visible region caused by nitrogen doping were responsible for the significant enhancement of OG degradation under visible light. In addition, the photosensitized oxidation mechanism originated from OG itself was also considered contributing to the higher visible-light-induced degradation efficiency. The effect of the initial pH of the solution and the dosage of hydrogen peroxide under different light sources was also investigated. Under visible light and sunlight, the optimal solution pH was both 2.0, while the optimal dosage of H₂O₂ was 5.0 and 15.0 mmol/l, respectively.     

POMs/ZrO2纳米可见光催化材料的制备及性能研究

多金属氧酸盐-氧化锆(POMs/ZrO2)复合材料是我们研制的一类具有可见光催化活性的新材料.本文结合可见光催化领域研究的最新进展,重点介绍POMs/ZrO2微孔纳米材料,包括它们的复合膜材料的制备、表征、表面物理特性、网络结构形成机理以及在可见光作用下对有机染料分子降解的光催化性能.     

Photocatalytic activity of novel AgBr/WO3 composite photocatalyst under visible light irradiation for methyl orange degradation

A novel AgBr/WO(3) composite photocatalyst was synthesized by loading AgBr on WO(3) substrate via deposition-precipitation method and characterized by XRD, SEM and DRS. The as-prepared AgBr/WO(3) was composed of monoclinic WO(3) substrate and face-centered cubic AgBr nanoparticles with crystalline sizes less than 56.8 nm. AgBr/WO(3) had absorption edge at about 470 nm in the visible light region. The optical AgBr content in AgBr/WO(3) was 0.30:1 (Ag/W) at the corresponding apparent rate, k(app), of 0.0160 min(-1) for MO degradation. The highest k(app) was 0.0216 min(-1) for 4 g/L catalyst. The OH acted as active species. Addition of H(2)O(2) within 0.020 mmol/L can efficiently trap electrons to generate more OH and further improved photocatalytic activity of AgBr/WO(3).     

Photocatalytic removal of phenol under visible light irradiation on zinc phthalocyanine/mesoporous carbon nitride nanocomposites

A series of zinc phthalocyanine/mesoporous carbon nitride (ZnPc/MCN) nanocomposites was prepared successfully by an impregnation method. The addition of ZnPc (0.05–1.5 wt%) extended the absorption of MCN to longer visible light region without affected its structure. It was found that the photocatalytic activity of the nanocomposites for phenol removal depended on the loading amount of ZnPc. The photocatalytic activity of the MCN increased as the amount of ZnPc increased to 0.05 wt%, but further increase in the loading amount decreased the activity. It was suggested that the optimum amount of ZnPc acted as a good photosensitiser that effectively induced electron charge transfer and reduced the electron-hole recombination.     

Photocatalytic activity of nitrogen doped rutile TiO2 nanoparticles under visible light irradiation

This work provides the design and synthesis of nitrogen doped rutile TiO₂ nanoparticles working as efficient photocatalysts under visible light irradiation. Nitrogen doped rutile TiO₂ nanoparticles are synthesized through the surface nitridation of rutile nanoparticles, which have been prepared in advance. The experimental results show that the nitrogen element is easily doped into the lattice of TiO₂ nanoparticles and its doping amount increases with the decrease of nanocrystallite size. The photocatalytic activity of the nanoparticles under visible light irradiation is correlated not only with the amount of doped nitrogen element but also with the morphology and crystallinity of nanoparticles.     

1D hierarchical CdS NPs/NiO NFs heterostructures with enhanced photocatalytic activity under visible light irradiation

One-dimensional (1D) hierarchically structured CdS nanoparticles (NPs)/NiO nanofibers (NFs) heterostructures with remarkable removal efficiency for diazo dye Congo red (CR) were fabricated by a stepwise synthesis process, which was involved a chemical bathing deposition combined with calcination, and a microwave-assisted wet chemical reaction. The crystal phases, morphologies, optical absorption properties, and adsorption/photocatalytic activity of as-prepared products were investigated by XRD, FESEM, TEM, high-resolution TEM (HRTEM), N₂ adsorption/desorption isotherms, UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectrum respectively. The experimental results indicated that binary satellite- core CdS NPs/NiO NFs heterojunctions are comprised of n-type CdS NPs with size of 10–30 nm decorated onto 1D p-type NiO NFs with diameter of 60–180 nm and length up to microns, which are self-assembled by nanoparticles with 30–100 nm in size. The possible formation mechanism for satellite-core structured CdS/NiO heterojunction is proposed. Interestingly, the decolorization efficiency over CdS/NiO heterostructures reached up to 91.2% in removal of aqueous CR at high concentration within 40 min under visible light irradiation, which was approximately 5.2 and 3.8 times as high as that of pure CdS nanocrystals (NCs) and the mixture of NiO NFs and CdS NCs. Furthermore, the possible photocatalytic mechanism was also investigated. The as-designed hybrid CdS NPs/NiO NFs heterostructures exhibited improved photocatalytic activity, which is attributed to the enhancement of the visible light adsorption, the efficient separation of photogenerated electrons and holes, and the high adsorption capacity towards CR molecules, thereby displaying superior visible- light-driven photodegradation of CR in high concentration. This work may provide a green engineering heterojunction technology to develop the advanced multifunctional nanocomposites for their applications in wastewater purification.     

铍、氮共掺杂TiO2的制备及其可见光下光解水制氢性能研究

通过煅烧硫酸钛与氨水水解沉淀物制备氮掺杂TiO2(N-TiO2),用浸渍法制备了铍、氮共掺杂TiO2光催化剂(Be-N-TiO2).通过可见光光还原沉积法载铂,以可见光(λ≥420nm)光催化制氢为探针反应考察了催化剂的活性,发现当煅烧温度为300℃,Be2 的掺杂量为1.5%(原子分数)时,制备的Pt/Be-N-TiO2制H2活性最高.通过XRD、DRS、FT-IR等手段对掺杂催化剂进行了表征,N掺杂可在TiO2中形成O-Ti-N键,使其具有可见光吸收能力;掺入Be2 可以有效的分离光生电子和空穴,减少了两者的复合,同时能够消除由于氮掺杂引入的氧空位,使共掺杂催化剂相对于单一的N-TiO2具有较高的可见光制H2活性.     

Photocatalytic performance of nanocrystalline Bi5Ti3FeO15 layered perovskite under visible light

Nanocrystalline Bi5Ti3FeO15 layered perovskite exhibiting Aurivillius phase was synthesized by polymerized complex (PC) method and investigated for its physico-chemical as well as optical properties. The crystallization of Bi5Ti3FeO15 synthesized by PC method was found to occur in the temperature range of 800-1050 degress C, whereas the single crystalline Bi5Ti3FeO15 formed at 1030 degrees C by solid state reaction (SSR) method. The observation of highly pure phase and such lower crystallization temperature in Bi5Ti3FeO15 prepared by PC method, is in total contrast to that observed in Bi5Ti3FeO15 prepared by the conventional solid-state reaction (SSR) method. The band gap of nanocrystalline Bi5Ti3FeO15 determined from UV-Vis diffusion reflectance spectrometer was 2.38 eV (525 nm). The photocatalytic activity of Pt/Bi5Ti3FeO15 prepared by PC method was investigated with the photodecomposition of isopropyl alcohol (IPA) and hydrogen production from water-methanol mixed solution under visible light (lambda > or = 420 nm). The respective activities for PC sample were higher than that of Pt/Bi5Ti3FeO15 prepared by SSR as well as Pt/TiO(2-x)N(x).     

Ag掺杂的K2La2Ti3O10可见光催化制氢的研究

采用高温固相法合成了具有可见光响应的Ag掺杂的K2La2Ti3O10催化剂,利用XRD、UV-VisDRS、TEM和XPS对催化剂进行了表征。考察了催化剂的可见光催化分解甲醇水溶液制氢的活性,并对可见光催化机理进行了分析。研究表明,Ag的掺杂没有改变K2La2Ti3O10的微晶结构,并使催化剂粒径有所减小。紫外-可见漫反射分析表明禁带宽度为2.8eV左右,对可见光具有较高吸收。担载2%(质量分数)Pt后,在可见光下光催化活性较K2La2Ti3O10大大提高,掺杂1%(摩尔分数)Ag的K2La2Ti3O10的产氢量为0.37mmol,而纯K2La2Ti3O10的产氢量只有0.037mmol;掺杂1%(摩尔分数)Ag的K2La2Ti3O10的产氢速率最大0.08mmol/h。     

Porous SnIn4S8 microspheres in a new polymorph that promotes dyes degradation under visible light irradiation

Porous SnIn(4)S(8) microspheres were initially synthesized through a facile solvothermal approach and were investigated as visible-light driven photocatalysts for dyes degradation in polluted water. The photocatalysts were characterized by XRD, SEM, TEM, N(2) adsorption-desorption, and UV-vis diffuse reflectance techniques. Results demonstrated that the as-synthesized SnIn(4)S(8) was of a new tetragonal polymorph, showing a band-gap of 2.5 eV, a specific surface area of 197 m(2) g(-1), and an accessible porous structure as well. The photocatalytic activity of the porous SnIn(4)S(8) was evaluated by decomposition of several typical organic dyes including methyl orange, rhodamine B, and methylene blue in aqueous solution under visible light irradiation. It is demonstrated that porous SnIn(4)S(8) was highly photoactive and stable for dyes degradation, showing photocatalytic activity much higher than binary constituent sulfides like In(2)S(3), SnS(2), or even ternary chalcogenide ZnIn(2)S(4) photocatalyst. The excellent photocatalytic performance of porous SnIn(4)S(8) is the consequence of its high surface area, well-defined porous texture, and large amount of hydroxyl radicals.     

Photocatalytic activity of vanadium-doped titania-activated carbon composite film under visible light

A V-doped titania-activated carbon composite film was prepared by a modified sol-gel method under mild condition. X-ray diffraction analysis revealed that the titania was a pure anatase phase. From scanning electron microscopy and N₂ adsorption-desorption measurements, we found that the composite film was porous since it formed a micro-nano structure. The photocatalytic activity of such film was evaluated through degradation of azo-dye Reactive Brilliant Red under visible light, and was compared to commercially available TiO₂, pure titania and vanadium-doped titania films. Results showed that the photocatalytic activity was enhanced a lot. It was due to expansion of the absorption edge by vanadium doping, and the synergistic effect of activated carbon with titania. Furthermore, the hydrophilic property of the as-prepared composite film was superior to other samples.     

Construction of hybrid g-C3N4/CdO nanocomposite with improved photodegradation activity of RhB dye under visible light irradiation

The hybrid graphitic carbon nitride-cadmium oxide (g-C₃N₄/CdO) nanocomposite was fabricated using chemical precipitation and self-assembly method. The photocatalysts were characterised by XRD, XPS, FTIR, BET, TEM, FESEM, UV-Vis and PL spectroscopy. Based on the optical study, visible light harvesting was improved and the band gap of bulk g-C₃N₄ to hybrid g-C₃N₄/CdO nanocomposite was greatly reduced from 2.72 eV to 2.35 eV, signifying a better charge carrier mobility. The photocatalytic activity were further assessed by conducting rhodamine B (RhB) photodegradation reaction using visible light. An excellent dye removal efficiency of 96% was achieved when 1.5 g/L of hybrid g-C₃N₄/CdO nanocomposite was used with an initial concentration of 10 ppm for 120 min whereas only 66% of RhB was removed by bulk g-C₃N₄ within the same operating conditions. Besides, reusability tests were carried out and evidenced that hybrid g-C₃N₄/CdO nanocomposite can be recycled up to four times by retaining the degradation efficiency. The scavenging studies confirmed that the RhB photodegradation using hybrid g-C₃N₄/CdO nanocomposite was controlled by valance band h⁺ and O²⁻ oxidation reactions. Conclusively, the inclusion of CdO onto g-C₃N₄ resulted in remarkable photocatalytic activity for dye degradation applications.     

Increasing the catalytic activities of iodine doped titanium dioxide by modifying with tin dioxide for the photodegradation of 2-chlorophenol under visible light irradiation

The photocatalytic degradation of 2-chlorophenol (2-CP) irradiated with visible light over iodine doped TiO(2) (IT) modified with SnO(2) (SIT) nanoparticles has been investigated in this study. The structure and optical properties of the SIT catalysts have been well characterized by X-ray diffraction, the Brunauer-Emmett-Teller method, transmission electron microscopy, UV-visible absorption spectra and X-ray photoelectron spectroscopy. The effects of preparation conditions, such as SnO(2) content and calcination temperature, on the photocatalytic degradation efficiency have been surveyed in detail. The improved photocatalytic activity of SIT is derived from the synergistic effect between the SnO(2) and IT, which promoted the efficiency of migration of the photogenerated carriers at the interface of the catalysts and thereby enhanced the efficiency of photon harvesting in the visible region. The action of scavengers (fluoride ion, iodide ion, tert-butyl alcohol, and persulfate ion), as well as N(2) purging on the photodegradation rate reveal that the valence band hole is mainly responsible for the effective photocatalytic removal of 2-CP and the corresponding TOC reduction.     

Copper-iron bimetal modified PAN fiber complexes as novel heterogeneous Fenton catalysts for degradation of organic dye under visible light irradiation

A series of Cu-Fe bimetal amidoximated polyacrylonitrile (PAN) fiber complexes with different molar ratios of Cu(2+) to Fe(3+) ions was prepared using a simple exhaustion method, and characterized using FTIR, DRS and XPS, respectively. Then they were tested as the heterogeneous Fenton catalysts for Rhodamine B degradation with H(2)O(2) in the dark and under visible light irradiation. The results indicated that Cu-Fe bimetal amidoximated PAN fiber complexes could more effectively catalyze the dye degradation in water than Fe amidoximated PAN fiber complex, especially in the dark. And introduction of Cu(2+) ions significantly increased their catalytic performance. 0.56 was the optimum molar ratio of Cu(2+) to Fe(3+) ions to achieve the best catalytic activity and stability. This was mainly due to the synergetic effect in the bimetal complexes. Visible light irradiation improved the catalytic activity of the complexes, especially with a low molar ratio of Cu(2+) to Fe(3+) ions.     

Photocatalytic activity of gallium nitride for producing hydrogen from water under light irradiation

Photocatalytic activity of powdered GaN for decomposing water into hydrogen under light irradiation was investigated. It was found that GaN has activity for producing hydrogen from water containing electron donors (Na₂S-Na₂SO₃, CH₃OH) without a loading of a noble metal; the obtained H₂ yield was ca. 150 μmol for a 200 h-Xe lamp (300 W) irradiation. The activity was increased by adding NaOH in the reaction solution due to the photo-etching of GaN by NaOH and concomitant removal of the native oxide from the surface, as confirmed by XPS, XRD, and PL measurements. The band energy scheme for GaN suggests that the conduction band edge of GaN is positioned at 0.5 V higher than the redox potential of H⁺/H₂. This large energy difference (overpotential) makes the photocatalytic H₂ evolution over GaN from water possible.     

Enhancement of photocatalytic H2 evolution on hexagonal CdS by a simple calcination method under visible light irradiation

An easy-handling calcination method has been used to eliminate the trap energy levels of hexagonal cadmium sulfide (CdS). The treated CdS exhibited extremely high photocatalytic activity for H₂ production under visible light irradiation. The rate of photocatalytic H₂ evolution has been dramatically enhanced by 55.8 times to 118 μmol h⁻¹ and further improved by 6.3 times to 749 μmol h⁻¹ after loading with 0.2 wt% Pt co-catalyst.     

Iron promotion of the TiO2 photosensitization process towards the photocatalytic oxidation of azo dyes under solar-simulated light irradiation

The photocatalytic oxidation of the azo dye Orange-II (Or-II) using Fe loaded TiO₂ (Fe–TiO₂) was studied under ultraviolet (UV), visible (vis) and simultaneous UV–vis irradiations using a solar light simulator. Photocatalysts were characterized by means of XRD, SEM-EDX, FTIR and DRS. Fe³⁺ species, identified in XPS analyses, were responsible of the increased absorption of visible light. Moreover, DRS analyses showed a decrease in the bandgap due to Fe³⁺ loading. Photocatalystic tests proved that Fe modification enhanced the TiO₂ photocatalytic activity towards Or-II photodegradation under simultaneous UV–vis irradiation. Even so, the performance of the Fe–TiO₂ samples towards the photodegradation of phenol, under UV irradiation, was lower than TiO₂ suggesting the recombination of the UV photogenerated electron–hole pair. Therefore, results evidence a Fe³⁺ promotion of the electron caption in the photosensitization process of TiO₂ by Or-II acting as a sensitizer. Such process leads to the Or-II photooxidation under UV–vis irradiation by losing energy in electron transferring processes to sensitize TiO₂, and, the formation of reactive oxygen species promoted by the injected electron to the TiO₂ conduction band.