圆盘状Bi2WO6-BiPO4异质结的水热合成及光催化性能 (cited: 1)

采用水热法制备Bi₂WO₆-BiPO₄异质结光催化剂．利用模拟太阳光照射下的罗丹明B降解实验评价了Bi₂WO₆-BiPO₄复合物的光催化性能．结果表明,Bi₂WO₆-BiPO₄光催化活性比Bi₂WO₆和BiPO₄高得多．当Bi₂WO₆与BiPO₄的摩尔比为1:1时复合光催化剂对罗丹明B的降解率最高．Bi₂WO₆-BiPO₄催化活性增强主要归结为两者之间形成了有效的异质结结构,其内建电场能够促进光生载流子的分离．同时,Bi₂WO₆的加入增强了其对可见光的吸收．研究表明O₂· ^-和h⁺在光催化降解过程中是主要的活性物种     

The effects of Gd3+ doping on the physical structure and photocatalytic performance of Bi2MoO6 nanoplate crystals

Gd³⁺ doped Bi₂MoO₆ nanoplate crystals were fabricated by solvothermal combined calcination method. The effects of Gd³⁺ doping with different concentrations on the texture, crystal and optical properties of Bi₂MoO₆ were investigated by N₂ physical adsorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet–visible diffuse reflection spectrum (UV–vis DRS), photoluminescence (PL) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Under simulated solar light irradiation, the influences of Gd³⁺doping on photocatalytic activity of Bi₂MoO₆ were evaluated by photocatalytic degradation of Rhodamine B. The characterization results showed that with Gd³⁺ doping, a contraction of lattice and a decrease in crystallite size occurred. Meanwhile, an increase in surface area over Gd³⁺ doped Bi₂MoO₆ was observed. Moreover, Gd³⁺ doping could obviously enhance the visible light harvesting of Bi₂MoO₆ and promoted the separation of photogenerated electrons and holes. With optimum Gd³⁺(6 wt%) doping, Gd/Bi₂MoO₆ exhibited the best activity and stability in degradation of Rhodamine B.     

Rapid sonochemical synthesis of irregular nanolaminar-like Bi2WO6 as efficient visible-light-active photocatalysts

Irregular Bi₂WO₆ nanolaminars have been successfully synthesized via a rapid sonochemical approach using bismuth nitrate and tungstic acid as precursors in an aqueous solution. The characteristics of them were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption, pore value, PL spectroscopy and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). These irregular nanolaminars are of geometric shapes of orthorhombic Bi₂WO₆ with their basal plane being (0 0 1). They possess high crystallinity, lager surface area and pore value, which means fewer traps and stronger photocatalytic activity. The growth mechanism of such special nanolaminar was related to the sonochemical synthesis route, which played a key role in the formation of Bi₂WO₆ nanolaminar. Simultaneously, it was found that the formation of Bi₂WO₆ nanolaminar is a time dependent process. The Bi₂WO₆ nanolaminar has higher photocatalytic activity than bulk Bi₂WO₆ nanoparticle obtained by refluxing method for rhodamine B (Rh.B) degradation under visible light irradiation (λ > 400 nm).     

A facile preparation strategy for hollow-structured Bi2O3/Bi2WO6 heterojunction with high visible light photocatalytic activity

A hollow-structured heterojunction consisting of Bi₂WO₆ nanoplatelets and Bi₂O₃ nanoparticles was successfully prepared by a facile solvothermal process. Bi₂O₃/Bi₂WO₆ heterojunction is the aggregate of some hollow spheres with diameter ranging from several hundred nanometers to 1.5 μm and is connected to each other by tube-like cavums. On the basis of scanning and transmission electron microscopy observation and X-ray diffraction analysis of the samples synthesized at different reaction stages, a possible growth mechanism was proposed for the growth of hollow-structured Bi₂O₃/Bi₂WO₆ heterojunction. Its photocatalytic activity was evaluated by degradation of rhodamine B under visible-light irradiation (λ>400 nm). The results indicate that the hollow-structured Bi₂O₃/Bi₂WO₆ heterojunction exhibits much higher photocatalytic activity than both pure Bi₂WO₆ and pure Bi₂O₃. The improved photocatalytic performance can be ascribed to the heterojunction of Bi₂O₃ and Bi₂WO₆ in the framework in which the hierarchical hollow structure possesses good permeability and large surface area. More importantly, the hollow-structured Bi₂O₃/Bi₂WO₆ heterojunction is not only highly stable but also easy to be separated by simple sedimentation for recycle.     

三元异质结构Ag-Bi2MoO6/BiPO4光催化剂高效降解苯酚红

多组分复合体系有利于电荷的有效分离,减少电子空穴对的复合几率。通过低温液相法首次合成Ag-Bi₂MoO₆/BiPO₄三元异质结构光催化剂。利用XRD、SEM、EDX及XPS等技术对样品进行了表征。结果表明,Ag纳米粒子光照积累在Bi₂MoO₆/BiPO₄的表面,通过表面等离子共振增加对可见光的吸收,同时作为电子受体促进了光生电子的转移。Ag、BiPO₄和Bi₂MoO₆形成三元异质结构有效地抑制了光生电子空穴对的复合。Ag-Bi₂MoO₆/BiPO₄表现出优异的光催化性能,其光催化活性较BiPO₄、Bi₂MoO₆和Bi₂MoO₆/BiPO₄样品有较大提高。并且对Ag-Bi₂MoO₆/BiPO₄三元异质结构的光催化机制进行了讨论。光催化过程中反应活性物种捕获实验结果表明h⁺和O₂^·-是主要的活性基团.     

g-C3N4 modified Bi2O3 composites with enhanced visible-light photocatalytic activity

Novel g-C₃N₄ modified Bi₂O₃ (g-C₃N₄/Bi₂O₃) composites were synthesized by a mixing-calcination method. The samples were characterized by thermogravimetry (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), UV–vis diffuse reflection spectroscopy (DRS), photoluminescence (PL) and photocurrent-time measurement (PT). The photocatalytic activity of the composites was evaluated by degradation of Rhodamine B (RHB) and 4-chlorophenol (4-CP) under visible light irradiation (>400 nm). The results indicated that the g-C₃N₄/Bi₂O₃ composites showed higher photocatalytic activity than that of Bi₂O₃ and g-C₃N₄. The enhanced photocatalytic activity of the g-C₃N₄/Bi₂O₃ composites could be attributed to the suitable band positions between g-C₃N₄ and Bi₂O₃. This leads to a low recombination between the photogenerated electron–hole pairs. The proposed mechanism for the enhanced visible-light photocatalytic activity of g-C₃N₄/Bi₂O₃ composites was proven by PL and PT analysis.     

Hydrothermal synthesis of graphitic carbon nitride–BiVO4 composites with enhanced visible light photocatalytic activities and the mechanism study

Novel graphitic carbon nitride (C₃N₄) and bismuth vanadate (BiVO₄) composite photocatalysts were successfully synthesized by a facile hydrothermal method. The scanning electron microscopy (SEM) revealed that an intimate interface between C₃N₄ and BiVO₄ formed in the composites. Compared with the pure C₃N₄ and BiVO₄, the C₃N₄–BiVO₄ photocatalysts showed remarkably the higher photocatalytic activities in degrading rhodamine B (Rh B). The best active heterojunction proportion was 0.5C₃N₄–0.5BiVO₄. Over this catalyst, the 100% degradation of Rh B (0.002 mmol L⁻¹) was obtained under visible light irradiation (λ>420 nm) for 40 min. The active species in Rh B degradation were examined by adding a series of scavengers. The study on photocatalytic mechanism revealed that the electrons injected directly from the conduction band of C₃N₄ to that of BiVO₄, resulting in the production of superoxide radical (O₂^•−) and hydroxyl radical (OH^•) in the conduction band of BiVO₄. Simultaneously, the rich holes in the valence band of g-C₃N₄ oxidized Rh B directly to promote the photocatalytic degradation reaction.     

Photocatalytic degradation of phenol over novel rod shaped Graphene@BiPO4 nanocomposite

Graphene@BiPO₄ nanocomposite with unique rod shape morphology of BiPO₄ has been successfully fabricated by the simple microwave assisted hydrothermal method. The crucial role of graphene oxide in the growth of rod shaped BiPO₄ crystals has been attempted to explain in this article. Graphene oxide acts as a structure-directing and morphology-controlling agent in the nucleation and growth of nanocrystals. The as prepared organic–inorganic hybrid Graphene@BiPO₄ nanocomposite photocatalyst was characterized by various techniques i.e. X-ray diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy, Raman spectroscopy and photoluminescence (PL) spectroscopy. The results were promising and shown enhanced photocatalytic activity than pure BiPO₄ for phenol degradation. The effect of graphene loading on the rates of photocatalytic degradation of phenol in solution is investigated. The result shows that the optimum photocatalytic activity of Graphene@BiPO₄ composite at 5 wt% of graphene under visible light is almost three times higher than pure BiPO₄.     

Synthesis and visible light photocatalysis water splitting property of chromium-doped Bi4Ti3O12

Photocatalysts Bi₄Ti_3 ? xCr_xO₁₂(x = 0.00, 0.06, 0.15, 0.30, 0.40, and 0.50) with perovskite structure were synthesized by sol–gel method and their electronic structures and photocatalytic activities were investigated. The Bi₄Ti_2.6Cr_0.4O₁₂ photocatalyst exhibited the highest performance of H₂ evolution in methanol aqueous solution (58.1 μmol h^? 1 g^? 1) under visible light irradiation (λ > 400 nm) without a co-catalyst, whereas no H₂ evolution is observed for Bi₄Ti₃O₁₂ under the same conditions. The UV–vis spectra indicated that the Bi₄Ti_2.6Cr_0.4O₁₂ had strong photoabsorption in the visible light region. The results of density functional theory (DFT) calculation illuminate that the conduction bands of Bi₄Ti₃O₁₂ are mainly attributable to the Ti 3d + Bi 6p orbitals, and the valence bands are composed of O 2p + Bi 6s hybrid orbitals, while the conduction bands of chromium-doped Bi₄Ti₃O₁₂ are mainly attributable to the Ti 3d + Bi 2p + Cr 3d orbitals, and the O 2p + Cr 3d hybrid obitals are the main contribution to the valence band.     

Anionic conductors Ln2/3[Bi12O14](MoO4)5 with Ln = La,Nd, Gd,Ho, Yb. Synthesis–spark plasma sintering–structure–electric properties

A new series of columnar phases Ln_2/3□_1/3[Bi₁₂O₁₄](MoO₄)₅ (□ vacancy) with Ln = La, Nd, Gd, Ho and Yb have been synthesized and structurally characterized. They feature the same formula as the molybdate phase Bi_2/3□_1/3[Bi₁₂O₁₄](MoO₄)₅ and crystallize in the monoclinic system, space group P2/c. These phases are isostructural with the prototype structure Bi[Bi₁₂O₁₄](MoO₄)₄(VO₄). Pellets of this rare-earth series obtained by spark plasma sintering and measured by impedance spectroscopy show a good anionic conductivity with a parabolic evolution whose maximum is raised by the Gd species at a determined value σ = 6.6 × 10^− 3 S cm^− 1 at 980 K.     

Hexamethylenetetramine assisted hydrothermal synthesis of BiPO4 and its electrochemical properties for supercapacitors

The well defined microstructures of BiPO₄ were successfully synthesized by the facile hexamethylenetetramine (HMT) assisted hydrothermal method. The low temperature monoclinic BiPO₄ structure with space group P2₁/n, were obtained from X-ray diffraction (XRD) for the pristine and HMT-assisted BiPO₄ with 1, 3, 5 and 10 mmole concentration. A transformation from low temperature monazite-type phase to the high temperature SbPO₄-type phase of BiPO₄ was observed at the 10 mmole concentration. There was a variation in the morphology from polyhedron to octahedra-like and finally into cube shape upon an increase in concentration of HMT. The role of reaction time in the morphology of BiPO₄ particles was investigated. The selected area electron diffraction (SAED) pattern elucidated the ordered dot pattern and the calculated d-spacing revealed the formation of BiPO₄. An increased specific capacitance of HMT assisted materials (202 F/g) compared with pristine BiPO₄ (89 F/g) at 5 mA/cm² was observed upon morphological variation due to HMT addition.     

Bi2MoO6纳米片/TiO2纳米棒阵列复合材料的制备及其可见光响应光电催化性能研究

Novel Bi₂MoO₆/TiO₂ heterojunction was fabricated by growing Bi₂MoO₆ nanosheets arrays on the vertically aligned TiO₂ nanorods arrays via a two-step solvothermal method. The obtained Bi₂MoO₆/TiO₂ hierarchical heterojunction showed excellent visible light photoelectrochemical performance. Compared with the pure TiO₂ and Bi₂MoO₆, the photocurrent density of the heterojunction was increased 57 and 29 times, respectively. Furthermore, the hydrogen generation rate of the Bi₂MoO₆/TiO₂ for photoelectrocatalytic water-splitting was about 6 times higher than that of the pure Bi₂MoO₆. The improved performance can be attributed to the synergistic effects of enhanced absorption of visible light, increase of migration rate and separation efficiency of photo-induced carriers.     

Structural,ferroelectric, optical properties of A-site-modified Bi0.5(Na0.78K0.22)0.5Ti0.97Zr0.03O3 lead-free piezoceramics

We reported the role of A-site modification on the structural, ferroelectric, optical and electrical field-induced strain properties of Bi_0.5(Na_0.78K_0.22)_0.5Ti_0.97Zr_0.03O₃ lead-free piezoceramics. The Li⁺ ions with concentration from 0 to 5 mol% were used to substitute at A-site. There was no phase transition when Li⁺ ions was added up to 5 mol%. The electric field-induced strain (S_max/E_max) values increased from 600 to 643 pm/V for 2 mol% Li⁺-added which results from distortion both rhombohedral and tetragonal phase structures. The band gap reduced from 2.88 to 2.68 eV and the saturation polarization decreased from 46.2 to 26.1 μC/cm² when Li⁺ ions concentration increased from 0 to 5 mol% respectively. We expect that this work could be helpful for further understanding the role of A-site dopants in comparison with B-site modification in lead-free Bi_0.5(Na,K)_0.5TiO₃-based ceramics.     

Wastewater treatment by sonophotocatalysis using PEG modified TiO2 film in a circular Photocatalytic-Ultrasonic system

TiO₂ photocatalyst film recently has been utilized as the potential candidate for the wastewater treatment, due to its high stability and low toxicity. In order to further increase the photocatalytic ability and stability, different molecular weight of polyethylene glycol (PEG) were used to modify TiO₂ structure to synthesize porous thin film used in the developed Photocatalytic-Ultrasonic system in this work. The results showed that PEG2000 modified TiO₂ calcinated under 450 °C for 2 h exhibited the highest photocatalytic activity, attributed to the smallest crystallite size and optimal particle size. Over 95.0% of rhodamine B (Rh B) was photocatalytically degraded by optimized PEG₂₀₀₀-TiO₂ film after 60 min of UV irradiation, while only about 50.8% of Rh B was decolored over pure TiO₂ film. Furthermore, optimized PEG₂₀₀₀-TiO₂ film was used in a circular Photocatalytic-Ultrasonic system, and the obtained synergy (0.6519) of sonophotocatalysis indicated its extremely high efficiency for Rh B degradation. In this Photocatalytic-Ultrasonic system, larger amount of PEG₂₀₀₀-TiO₂ coated glass beads, stronger ultrasonic power and longer experimental time could result to higher degradation efficiency of Rh B. In addition, repetitive experiments showed that about 97.2% of Rh B were still degraded in the fifth experiment by sonophotocatalysis using PEG₂₀₀₀-TiO₂ film. Therefore, PEG₂₀₀₀-TiO₂ film used in Photocatalytic-Ultrasonic system has promising potential for wastewater treatment, due to its excellent photocatalytic activity and high stability.     

Synthesis of TiO2/WO3 nanoparticles via sonochemical approach for the photocatalytic degradation of methylene blue under visible light illumination

Through an ultrasound assisted method, TiO₂/WO₃ nanoparticles were synthesized at room temperature. The XRD pattern of as-prepared TiO₂/WO₃ nanoparticles matches well with that of pure monoclinic WO₃ and rutile TiO₂ nanoparticles. TEM images show that the prepared TiO₂/WO₃ nanoparticles consist of mixed square and hexagonal shape particles about 8–12 nm in diameter. The photocatalytic activity of TiO₂/WO₃ nanoparticles was tested for the degradation of a wastewater containing methylene blue (MB) under visible light illumination. The TiO₂/WO₃ nanoparticles exhibits a higher degradation rate constant (6.72 × 10⁻⁴ s⁻¹) than bare TiO₂ nanoparticles (1.72 × 10⁻⁴ s⁻¹) under similar experimental conditions.     

Preparation, characterization and photocatalytic activity of polycrystalline Bi2O3/SrTiO3 composite powders

Bi₂O₃/SrTiO₃ composite powders have been prepared and their photocatalytic activities were investigated by photooxidation of methanol. These powders were characterized by UV-Visible diffuse reflectance spectra, SEM and X-ray diffraction (XRD). The results revealed that all the Bi₂O₃/SrTiO₃ composite powders exhibited higher photocatalytic activity than pure SrTiO₃, Bi₂O₃ and TiO₂ (P25) under visible light irradiation (λ>440 nm). The effects of the Bi₂O₃ contents on the photocatalytic activities of the composite powders were examined, the photocatalytic activities increased with the content of Bi₂O₃ increasing to a maximum of 83% and then decreased under visible light irradiation. The effects of the calcination temperatures on the photocatalytic activities of the composite powders were also investigated.     

Photoluminescence characterization of a novel red-emitting phosphor In2(MoO4)3:Eu3+ for white light emitting diodes

The red-emitting phosphor In₂(MoO₄)₃:Eu³⁺ with cubic crystal structure was synthesized by a conventional solid-state reaction technique and its photoluminescence properties were investigated. The prepared phosphor can be efficiently excited by ultraviolet (395 nm) and blue (466 nm) light. The emission spectra of the phosphor manifest intensive red-emitting lines at 612 nm due to the electric dipole ⁵D₀→⁷F₂ transitions of Eu³⁺. The chromaticity coordinates of x=0.63, y=0.35 (λ_ex=395 nm) and x=0.60, y=0.38 (λ_ex=466 nm) are close to the standard of National Television Standard Committee values (NTSC) values. The concentration quenching of In₂(MoO₄)₃:Eu³⁺ is 40 mol% and the concentration self-quenching mechanism under 466 nm excitation was the dd intereaction. As a result of the strong emission intensity and good excitation, the phosphor In₂(MoO₄)₃:Eu³⁺ is regarded as a promising red-emitting conversion material for white LEDs.     

Structure Tuning of Bi2MoO6 and Their Enhanced Visible Light Photocatalytic Performances

Structure-tuning strategies for synthesis and modification of Bi₂MoO₆, a novel visible light photocatalyst, have progressed at a quick pace. The enhancement of photocatalytic performances has been obtained through several morphology controls including hierarchical structures and heterojunctional nanocomposites. In this article, various structure modifications and their structural advantages in photocatalysis will be reviewed. In the first section, the structures of Bi₂MoO₆ such as crystal structures, electronic structures, and band structures will be presented. In the second section, many controllable synthesis approaches for modification of Bi₂MoO₆, including solid-state reaction, co-precipitation, solvothermal, and hydrothermal methods will be introduced. In the last section, the enhancement of photocatalytic activity for Bi₂MoO₆ due to the structure tuning will be discussed. The comprehensive review will provide perspectives on the research of efficient photocatalysts under visible light irradiation.     

Synthesis of β-Bi2O3 towards the application of photocatalytic degradation of methyl orange and its instability

Bismuth oxide carbonate was synthesized from bismuth nitrate and potassium carbonate and then converted to phase pure β-Bi₂O₃ form by means of thermal decomposition. X-ray diffraction, HR-SEM, diffuse reflectance UV–vis and photocatalytic degradation studies were carried out on both the samples. Bi₂O₂CO₃ exhibited a wide band gap of 3.406(5) eV while β-Bi₂O₃ had a lesser band gap of 2.589(3) eV. β-Bi₂O₃ degrades a higher amount of methyl orange because of its lesser band gap and its optimum loading was 0.1 g in 50 ml of 10 ppm solution. After photocatalytic degradation Bi₂O₂CO₃ remains in the stable form whereas β-Bi₂O₃ changes to Bi₂O₂CO₃.     

Fabrication of Fe-doped TiO2 nanoparticles and investigation of photocatalytic decolorization of reactive red 198 under visible light irradiation

In this research, Fe-doped TiO₂ nanoparticles with various Fe concentrations (0. 0.1, 1, 5 and 10 wt%) were prepared by a sol–gel method. Then, nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDX), BET surface area, photoluminescence (PL) spectroscopy and UV–vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the nano-particles was evaluated through degradation of reactive red 198 (RR 198) under UV and visible light irradiations. XRD results revealed that all samples contained only anatase phase. DRS showed that the Fe doping in the titania induced a significant red shift of the absorption edge and then the band gap energy decreased from 3 to 2.1 eV. Photocatalytic results indicated that TiO₂ had a highest photocatalytic decolorization of the RR 198 under UV irradiation whereas photocatalytic decolorization of the RR 198 under visible irradiation increased in the presence of Fe-doped TiO₂ nanoparticles. Among the samples, Fe-1 wt% doped TiO₂ nanoparticles showed the highest photocatalytic decolorization of RR198 under visible light irradiation.