Efficient photocatalytic activity of water oxidation over WO3/BiVO4 composite under visible light irradiation

A coupled WO₃/BiVO₄ thin film has been deposited on FTO substrate by a spin coating method from precursor solutions. The composite films were characterized by AFM, SEM, XPS and XRD techniques. The incident photon to current efficiency (IPCE) of BiVO₄ electrode was increased by 10 times when a WO₃ film was layered between the BiVO₄ layer and the FTO substrate. The enhanced performance of WO₃/BiVO₄ composite film electrode is mainly ascribed to the effective electron-hole separations at the semiconductor heterojunction. A schematic mechanism of charge transfer was proposed to explain the photocurrent enhancement for the WO₃/BiVO₄ electrode surface.     

Properties of sol-gel SnO2/TiO2 electrodes and their photoelectrocatalytic activities under UV and visible light illumination

A visible light active binary SnO₂-TiO₂ composite was successfully prepared by a sol-gel method and deposited on Ti sheet as a photoanode to degrade orange II dye. Titanium and SnO₂ can promote the development of rutile phase of TiO₂ and inhibit the formation of anatase phase of TiO₂. Formation of SnO₂ crystalline is insignificant even when the calcination temperature increases to 700 °C. Heterogenized interface between SnO₂ and TiO₂ inhibits growth of TiO₂ linkage and leads to the particle-filled surface morphology of SnO₂-containing films. The carbonaceous, Ti-O-C bonds and Ti³⁺ species are likely to account for the photoabsorption and photoelectrocatalytic (PEC) activity under visible light illumination. The electrode with 30% SnO₂ exhibits higher photocurrent when compared with those in the region of 0-50%. The 600 °C-calcined SnO₂-TiO₂ electrode indicates higher activity when compared with those at 400, 500, 700 and 800 °C. PEC degradation of orange II follows the Langmuir-Hinshelwood model and takes place much effectively in a solution of pH 3.0 than those in pH 7.0 and pH 11.0.     

A temperature-responsive polyurethane film with reversible visible light transmittance change and constant low UV light transmittance

We prepared a temperature-responsive polyurethane (PU) film with reversible visible light transmittance change, which was opaque at room temperature and became transparent when the temperature rised. The PU film has very low visible light transmittance of 1.4% at room temperature. At 45 °C, the PU film has relatively high transmittance of 66.7% looking translucent. When the temperature goes to 50 °C or above, the transmittance is more than 80% and the PU film is transparent. The reason for this interesting phenomenon about visible light transmittance change was illustrated by polarizing optical microscope and differential scanning calorimetry. While ultraviolet light transmittance of the PU film is very low at all time. Moreover, this PU film has excellent mechanical performance in a wide temperature range. We suppose this PU film has potential applications in many fields such as tunable optical devices or coating materials with smart temperature responsivity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47140.     

Tb掺杂介孔TiO_2/聚噻吩复合材料的制备及其可见光光催化性能研究

采用原位聚合法制备了一系列不同质量比m(Th)/m(Tb掺杂介孔TiO2)的复合光催化剂(其中Th为噻吩),采用XRD、FTIR、荧光光谱(PL)、场发射透射电镜(FETEM)和X射线光电子能谱(XPS)对复合光催化剂进行了表征。结果表明,复合粒子上的聚噻吩骨架中S原子与TiO2粒子间存在相互作用。以罗丹明B为模型降解物,研究了不同比例复合光催化剂在可见光下的光催化性能,其中m(Th)/m(Tb掺杂介孔TiO2)=1/10复合光催化剂光催化性能最好。在可见光照射下4 h,脱色率达到82.4%。这是由于Tb掺杂介孔TiO2与PTh(聚噻吩)之间的协同作用,拓宽了TiO2纳米粒子的光响应范围,提高了光生电子和空穴的分离效率,从而有效提高了其光催化性能。     

Efficient decomposition of organic compounds with FeTiO3/TiO2 heterojunction under visible light irradiation

FeTiO₃/TiO₂, a new heterojunction-type photocatalyst working at visible light, was prepared by a simple sol–gel method. Not only did FeTiO₃/TiO₂ exhibit greatly enhanced photocatalytic activity in decomposing 2-propanol in gas phase and 4-chlorophenol in aqueous solution, but also it induced efficient mineralization of 2-propanol under visible light irradiation (λ ≥ 420 nm). Furthermore, it showed a good photochemical stability in repeated photocatalytic applications. FeTiO₃ showed a profound absorption over the entire visible range, and its valence band (VB) position is close to that of TiO₂. The unusually high photocatalytic efficiency of the FeTiO₃/TiO₂ composite was therefore deduced to be caused by hole transfer between the VB of FeTiO₃ and TiO₂.     

Photocatalytic O2 evolution under visible light irradiation on BiVO4 in aqueous AgNO3 solution

BiVO₄ with a 2.3 eV band gap showed an activity for O₂ evolution from aqueous solutions containing Ag⁺ as an electron scavenger under visible light irradiation (λ > 520 nm). The quantum yield was 0.5% at 450 nm. This revised version was published online in July 2006 with corrections to the Cover Date.     

Enhanced photoelectrocatalytic activity of FTO/WO3/BiVO4 electrode modified with gold nanoparticles for water oxidation under visible light irradiation

Gold nanoparticles were successfully deposited on FTO/WO₃/BiVO₄ electrode surface by means of electrolysis of AuCl₄⁻ ions. The composite films were characterized by SEM, XPS and XRD techniques. An increase in photocurrent and a negative shift of onset potential for water oxidation were observed upon modification of the electrode surface with the Au particles. The electrochemical impedance spectroscopy was used to confirm the acceleration of charge transfer process by Au deposition at the electrode surface. The photocurrent action spectrum did not correlate with the plasmonic absorbance of Au nanoparticles at 560 nm, suggesting that the Au nanoparticles increased charge separation without undergoing a plasmon resonance effect under visible light irradiation.     

High photostrictive efficiency of Mg3V2O8 ceramics under visible light illumination

The materials showing significant photostrictive effect under visible light are of great interest for the development of advanced micro-optomechanical systems (MOMS). Till date, ferroelectrics have remained the most widely investigated materials for photostriction, but due to wide bandgap their efficiency remains poor in visible light. Herein, magnesium orthovandate (Mg₃V₂O₈) ceramics, showing a bandgap of 2.43 eV, is demonstrated for significant photostrictive efficiency (η) under visible light. In the illumination of laser  655 nm, it shows η = 1.5 × 10⁻¹¹ m³/W, the highest efficiency ever reported for any ceramic under visible light, and under laser405 nm, shows η = 1.0 × 10⁻¹¹ m³/W, the efficiency higher than most of the reported materials in similar illumination conditions. The in situ X-ray diffraction patterns collected under external laser illumination in conjunction with power dependent Raman spectroscopy indicates that the photostriction of Mg₃V₂O₈ ceramics is attributed to light induced distortion of its VO₄ tetrahedrons and MgO₆ octahedrons. Whilst, comparative analysis of Raman modes identified experimentally and modes calculated by density functional theory reveals that the light-triggered electron–phonon resonating interactions and light-induced phase transition are the most likely origin of large polyhedral distortions and hence higher value of η at specific light intensity of lasers 655 and 405 nm, respectively. These results show considerable advantage of Mg₃V₂O₈ ceramics for MOMS and other light-driven applications.     

Removal of persistent tartrazine dye by photodegradation on TiO2 nanoparticles enhanced by immobilized calcinated sewage sludge under visible light

TiO₂ nanoparticles on calcined sewage sludge (TiO₂/sludge) were prepared by the sol-gel method and were fully characterized. The photocatalytic efficiency of TiO₂/sludge was evaluated by tartrazine dye degradation by halide lamp. TiO₂/sludge exhibited a high photocatalytic oxidation efficiency (more than 90%) of tartrazine compared with naked TiO₂ (less than 20%) due to the synergy effect of sewage sludge. The optimization of experimental conditions was 0.5 g/l TiO₂/Sludge, pH 8 with 50 mg/l tartrazine dye. The addition of sewage sludge to TiO₂ improves the efficiency of dye mineralization. The prepared catalyst showed easier separation and effective reuse.     

Simple fabrication of N-doped mesoporous TiO2 nanorods with the enhanced visible light photocatalytic activity

N-doped mesoporous TiO₂ nanorods were fabricated by a modified and facile sol–gel approach without any templates. Ammonium nitrate was used as a raw source of N dopants, which could produce a lot of gasses such as N₂, NO₂, and H₂O in the process of heating samples. These gasses were proved to be vitally important to form the special mesoporous structure. The samples were characterized by the powder X-ray diffraction, X-ray photoelectron spectrometer, nitrogen adsorption isotherms, scanning electron microscopy, transmission electron microscopy, and UV-visible absorption spectra. The average length and the cross section diameter of the as-prepared samples were ca. 1.5 μm and ca. 80 nm, respectively. The photocatalytic activity was evaluated by photodegradation of methylene blue (MB) in aqueous solution. The N-doped mesoporous TiO₂ nanorods showed an excellent photocatalytic activity, which may be attributed to the enlarged surface area (106.4 m² g^-1) and the narrowed band gap (2.05 eV). Besides, the rod-like photocatalyst was found to be easy to recycle.     

Preparation and characterization of PVC/CsxWO3 composite film with excellent near-infrared light shielding and high visible light transmission

Near-infrared (NIR) shielding is essential not only in the building and automobile glass films but also in achieving energy conservation. However, effectively shielding NIR and maintaining high transmittance in the visible light region have been great challenges in the past decade. Recently, hexagonal cesium tungsten bronze (Cs_xWO₃) nanoparticles have been widely studied due to the excellent transparency in the visible light region and strong heat-shielding ability in the NIR region. Herein, a design concept of transparent polyvinyl chloride (PVC)/Cs_xWO₃ composite film, as a heat insulation material for glasses, was proposed. To achieve this purpose, the PVC/Cs_xWO₃ composite film was prepared by incorporating Cs_xWO₃ slurry with better dispersion than traditional Cs_xWO₃ nanoparticles powder into a transparent PVC matrix. By the UV-Vis-NIR spectrophotometer characterization, the PVC/Cs_xWO₃ composite film containing 2.1 phr Cs_xWO₃ slurry displays high blocking of NIR (78%) and high transmittance of visible light (76%). In order to further understand the actual heat insulation effect from the PVC/Cs_xWO₃ composite films, the indoor sunlight simulation test and outdoor cooling experiment with solar illumination variations were carried out, which both showed heat insulation that is superior to the antimony tin oxide and indium tin oxide thin films prepared in our previous work. In addition, the mechanical property of PVC/Cs_xWO₃ composite films shows almost no change with the increase of Cs_xWO₃ slurry. The PVC/Cs_xWO₃ composite films simultaneously achieve excellent shielding of NIR and high transmittance of visible light, which makes it an ideal material to alleviate the current building energy consumption issues.     

Preparation and characterisation of visible light responsive iodine doped TiO2 electrodes

Characteristics are presented of new iodine doped TiO₂ (I-TiO₂) prepared via the hydrothermal method, where titania (IV) complexes with a ligand containing an iodine atom have been used as a precursor. The structure of samples has been examined by XPS, XRD, UV-vis and FT-IR-ATR techniques. These studies confirm that the obtained powder exhibits a decrease in the bandgap energy value (E_g = 2.8 eV). The report presents electrochemical studies of I-TiO₂ films on a Pt electrode, which allow determination of the flatband potential E_fb = −0.437 V vs. SCE (in 0.5 M Na₂SO₄). Cyclic voltammetry measurements show anodic and cathodic activities under Vis and UV-vis radiation. The photocurrent enhancement due to visible light radiation reached 30% of the whole photoacitivity exhibited under UV-vis illumination.     

Photocatalytic H2 evolution under visible light irradiation on Zn1-x Cu x S solid solution

The H₂ evolution reaction from an aqueous Na₂SO₃ solution proceeded with 3.7% quantum yield under visible light irradiation (λ > 420 nm) on a Zn_0.957Cu_0.043S solid solution photocatalyst without co‐catalysts such as Pt. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ag-TiO2多孔薄膜及其非紫外光辐照下的超亲水特性

采用溶胶凝胶法，以钛酸丁酯为前驱体、硝酸银络合物为银源、聚乙二醇2000（PEG2000）作为结构导向剂，制备超亲水多孔Ag-TiO₂复合薄膜。用X射线衍射仪、X射线光电子能谱仪、扫描电镜、原子力显微镜表征薄膜晶相结构、化学成分以及表面形貌。根据静态水接触角、动态润湿时间、超亲水长效稳定性综合评价不同Ag含量及PEG2000添加量薄膜的超亲水性能。研究发现，掺杂Ag与PEG2000对薄膜在非紫外光下的超亲水特性具有协同作用，掺杂Ag明显提高薄膜动态润湿速度及可见光响应，表面粗糙多孔结构有利于避光条件下的长效超亲水特性。Ag含量10%、PEG2000掺杂量5%的Ag-TiO₂复合薄膜在自然光条件下已具备优良的超亲水性能；水滴0.2 s内即可在表面完全铺展到0°；避光条件下保存，超亲水时效性可达到30 d以上。在可见光活化下即可强化超亲水性能，具有良好的防雾效果。     

Enhanced visible light photocatalytic activity of QDS modified Bi2WO6 nanostructures

Bi₂WO₆ (BWO) nanostructures with QDS dispersed on single crystalline nanosheets were successfully prepared by a facile solvothermal method. The product possessed large surface area of 60 m²/g and exhibited excellent visible light absorption with a blue shift from 2.54 eV to 2.75 eV. The photocatalytic efficiency of the sample was six times that of nanoparticles assembled BWO nanostructures and three times that of nanoplates assembled BWO nanostructures. The photocatalytic mechanism for degradation of dyes over QDS modified BWO nanostructures was discussed, which revealed the important role of QDS in the generation, migration and consumption of the photogenerated electrons and holes.     

Preparation of hollow porous Cu2O microspheres and photocatalytic activity under visible light irradiation

Cu₂O p-type semiconductor hollow porous microspheres have been prepared by using a simple soft-template method at room temperature. The morphology of as-synthesized samples is hollow spherical structures with the diameter ranging from 200 to 500 nm, and the surfaces of the spheres are rough, porous and with lots of channels and folds. The photocatalytic activity of degradation of methyl orange (MO) under visible light irradiation was investigated by UV-visible spectroscopy. The results show that the hollow porous Cu₂O particles were uniform in diameters and have an excellent ability in visible light-induced degradation of MO. Meanwhile, the growth mechanism of the prepared Cu₂O was also analyzed. We find that sodium dodecyl sulfate acted the role of soft templates in the synthesis process. The hollow porous structure was not only sensitive to the soft template but also to the amount of reagents.     

Photooxidation of organic compounds in a solution containing hydrogen peroxide and TiO2 particles under visible light

Cyclohexane was oxidized under visible light in a titanium dioxide suspension containing hydrogen peroxide. Cyclohexanol and cyclohexanone were detected as products. Under similar experimental conditions, nonyl aldehyde was oxidized to nonylic acid. The reaction rate for the oxidation on rutile particles was faster than that on anatase particles. When hydrogen peroxide was added to suspensions of these particles, both rutile and anatase particles became yellow-colored due to the formation of peroxide complexes on their surfaces. The difference between the reaction rates for rutile and anatase particles suggests that the properties of the peroxide complexes formed on these particles are different. The properties of these complexes were studied by UV–vis spectroscopy.