Investigation of photocatalytic activities over Bi₂WO₆/ZnWO₄ composite under UV light and its photoinduced charge transfer properties

Bi(2)WO(6)/ZnWO(4) composite photocatalysts have been successfully synthesized by a facile hydrothermal process. The catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microcopy (TEM), and UV-vis diffuse reflectance spectrum (DRS). The results show that Bi(2)WO(6) nanoparticles grow on the primary ZnWO(4) nanorods. The Bi(2)WO(6)/ZnWO(4) composites have better UV light photocatalytic activities compared to single ZnWO(4) nanorods. Furthermore, the photoinduced charge transfer properties of Bi(2)WO(6)/ZnWO(4) composites were investigated by means of transient photovoltage (TPV) technique in detail. The interconnected interface of Bi(2)WO(6)/ZnWO(4) composites led to the low recombination ratios of photoinduced electron-hole pairs and enhanced photocatalytic activities.     

Graphite oxide-assisted sonochemical preparation of α-Bi2O3 nanosheets and their high-efficiency visible light photocatalytic activity

Novel α-Bi₂O₃ nanosheets have been successfully synthesized by graphite oxide (GO)-assisted sonochemical route and subsequent calcining treatment. The morphology of the final products can be controlled by tuning GO nanosheets in the synthesis process. Porous and nanosheet-covered α-Bi₂O₃ microrods have also been obtained, and the growth mechanism has been discussed. Scanning electron microscopy and transmission electron microscopy analyses reveal that the α-Bi₂O₃ nanosheets are 10–20 nm in thickness with suppressed growth along the [2 1 ?4] direction. Owing to the unique structure, the α-Bi₂O₃ nanosheets show broader optical absorption and narrower band gap (2.25 eV) as compared to other two forms of α-Bi₂O₃ (~2.8 eV). Photocatalytic experiments demonstrated that the α-Bi₂O₃ nanosheets exhibited excellent activity much higher than the porous and nanosheet-covered α-Bi₂O₃ microrods in degrading organic pollutants under visible light. This study opens up a new route for the preparation of α-Bi₂O₃ nanosheets with superior photocatalytic performance.     

Room-temperature resistive H₂ sensing response of Pd/WO₃ nanocluster-based highly porous film

Hydrogen- (H?-) induced resistive response of palladium (Pd) coated tungsten oxide (WO?) films prepared by using supersonic cluster beam deposition (SCBD) was investigated. An SCBD WO? film is found to be constructed of WO? nanoclusters of diameters of 3-5 nm. The nanoclusters are loosely connected to form a structure of high porosity around 66%. With this structure, the film exhibits many excellent room-temperature H? sensing properties, including high sensitivity, broad detectable range of H? concentration, low detection limit, fast response rate, excellent cyclic stability (>2400 cycles), high selectivity against vapor of many organic compounds, mild ambient pressure dependence and many other advantages such as low power consumption, miniaturizability and high batch-to-batch reproducibility. These findings are useful for making new high-quality H? sensors for monitoring the leakage of H? and ensuring safe use of this gas.     

Investigations on the photocatalytic activity of sol–gel derived plain and Fe/Nb-doped titania coatings on glass substrates

Plain and doped (Fe³⁺ and Nb⁵⁺) titania coatings were deposited by dip coating on soda lime glass substrates using titania sol synthesized by sol–gel route in combination with commercial nanoparticle dispersions. The dopant concentrations were fixed at 0.07 wt% and the coatings heat treated at 400 °C were characterized with respect to their thickness, phase composition, hydrophilicity/hydrophobicity and microstructure. Photocatalytic activity testing was carried out on the coatings by following up the degradation of methylene blue dye for up to 4 h at 1 h time intervals after exposure to sunlight. The effect of a trivalent and pentavalent doping of Ti⁴⁺ sites on photocatalytic activity of TiO₂ was investigated.     

Influence of platinum nano-particles on the photocatalytic activity of sol–gel derived TiO2 films

Different 1-step or 2-step photo-platinization methods have been implemented to load sol–gel TiO₂ photocatalytic thin films with platinum nano-particles. These methods enable flexible variations in the amount of loaded particles, and they strongly influence the structure and size of these particles and the morphology of derived platinized films. The photocatalytic activity of platinized films has been studied. It is shown that optimal platinization conditions allow envisaging thin film photocatalysts with enhanced properties. Best performances are reached when the films are loaded with platinum particles for 30 or 60 min using a 1-step platinization method, which yields photocatalytic activities about 4 times greater than that of non-platinized films. Photocatalytic activity differences induced by the 1-step or 2-step photo-platinization methods are discussed in relation to the amount of loaded platinum together with structural and morphological features.     

Impact of Pt loading methods over mesoporous-assembled TiO2–ZrO2 mixed oxide nanocrystal on photocatalytic dye-sensitized H2 production activity

In this work, the photocatalytic water splitting under visible light irradiation for hydrogen production was investigated by using Eosin Y-sensitized Pt-loaded mesoporous-assembled TiO₂–ZrO₂ mixed oxide nanocrystal photocatalysts. The mesoporous-assembled TiO₂–ZrO₂ mixed oxide with the TiO₂-to-ZrO₂ molar ratio of 95:5 (i.e. 0.95TiO₂–0.05ZrO₂) was synthesized by using a sol–gel process with the aid of a structure-directing surfactant. The Pt loading was comparatively performed via two different effective methods: single-step sol–gel (SSSG) and photochemical deposition (PCD). The synthesized photocatalysts were methodically characterized by N₂ adsorption–desorption, XRD, UV–visible spectroscopy, SEM–EDX, TEM–EDX, TPR, and H₂ chemisorption analyses. The results revealed that the Pt loading by the PCD method greatly enhanced the photocatalytic hydrogen production activity of the synthesized mesoporous-assembled 0.95TiO₂–0.05ZrO₂ mixed oxide photocatalyst more than that by the SSSG method. The optimum Pt loading by the PCD method was experimentally observed at 0.5 wt.%, which was well associated with the maximum Pt dispersion. In addition, the PCD conditions, i.e. UV light irradiation time and UV light intensity, were investigated and optimized to be 2 h and 44 W, respectively.     

Weighting the influence of TiO2 anatase/brookite ratio in TiO2–Ag porous nanocomposites on visible photocatalytic performances

Nanocomposites based on TiO₂ aerogel and Ag nanoparticles have been successfully obtained through different synthesis methods and their specific surface areas have been determined by N₂ sorption (BET method). The photocatalytic potential for salicylic acid degradation has been evaluated. It was found that under visible light irradiation, all synthesized nanocomposites exhibit higher photocatalytic activity than the commercially available Aeroxide P25. By correlating the structural parameters with the photocatalytic performances, it has been found that the Ag nanoparticles and brookite phase presence alongside the anatase play important roles on the visible photocatalysts behavior. For the Ag containing samples with mixed anatase–brookite phases, it has been observed that the visible photocatalytic performance decreases with the increase in brookite crystalline phase content. On the other hand, the addition of Ag nanoparticles results, as expected, in a clear enhancement of the visible photocatalytic activity.     

Cu7.2S4 nanosheets decorated on the {3 3 2} high index facets of Cu2O with controllable oxygen defects and enhanced photocatalytic activity

The heterostructure of Cu_7.2S₄ nanosheets/trisoctahedron Cu₂O were successfully constructed on the {3 3 2} high-index facets of Cu₂O. The results show that oxygen defects amount of the Cu_7.2S₄/Cu₂O samples are closely related to the thickness of Cu_7.2S₄ nanosheets. Compared with the unmodified cuprous oxide and the Cu_7.2S₄/Cu₂O modified with thick Cu_7.2S₄ nanosheets, the Cu_7.2S₄/Cu₂O grafted with 10 nm thickness of Cu_7.2S₄ show higher oxygen defects content and photocatalytic performance for MO decoloration. UV–VIS DRS and PL detection show that the Cu_7.2S₄ nanosheets grafting on Cu₂O with high-index facets accelerates the charge carrier separation, which results in an elevated degradation properties for MO.     

EPR,DFT, and Mott–Schottky study on visible light photocatalytic activity of Au and Co3O4 mediated Bi2WO6: role of SPR and multi-valence states

Journal of Materials Science: Materials in Electronics - Au nanoparticles modified p–n hetero-structured Co3O4/Bi2WO6 composites was synthesized in present paper, and the photocatalytic...     

Influence of lanthanum precursors on the heterogeneous La/SnO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript> nanocatalyst with enhanced catalytic activity under visible light

Surfactant controlled synthesis of La/SnO₂–TiO₂ nanocomposite was studied by using anionic surfactant dioctyl sulfosuccinate sodium salt (DOSS) synthesized via sol–gel method followed by hydrothermal method by using different lanthanum precursors. The structural investigation, thermal degradation, kinetics, thermodynamics properties, crystallite size, morphology, surface and photocatalytic properties of synthesized samples were studied by using different characterization techniques i.e. Thermogravimetric analysis (TGA), Fourier transform-infrared spectroscopy (FTIR), Particle Size Analyzer (PSA), Powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Ultraviolet–Visible spectrophotometer (UV–VIS). Band gap calculations and optical properties of both SnO₂–TiO₂ and La/SnO₂–TiO₂ were studied by using UV–Visible spectroscopy. The performance of both SnO₂–TiO₂ and La/SnO₂–TiO₂ nanocomposites as a photocatalytic agent was also investigated for the degradation of methylene blue (MB) under the illumination of sunlight.