Ag/BiOX(X=Cl,Br,I)复合光催化剂的制备、表征及其光催化性能

采用光化学沉积法制备了一系列不同Ag含量的新型Ag/BiOX(X=Cl,Br,I)复合光催化剂,应用X射线粉末衍射(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)、光致发光(PL)谱、紫外-可见(UV-Vis)光谱和N2物理吸附等手段对催化剂进行表征,并以420nm<λ<660nm的可见光为光源,评价了该催化剂光催化降解酸性橙II的活性,考察了不同含量的Ag沉积对BiOX样品光催化性能的影响.N2物理吸附测试结果表明,沉积银在一定程度降低了催化剂的比表面积.UV-Vis测试结果表明,Ag能产生表面等离子共振吸收,有效增强BiOCl和BiOBr对可见光的吸收能力.PL测试结果则表明,Ag能显著抑制光生电子(e-)和空穴(h+)的复合.Ag的存在大幅度提高了BiOX对染料的光催化降解活性.当负载Ag的质量分数(w)为1%-2%时,可使BiOCl、BiOBr和BiOI光催化活性分别提高了10、13和2倍.Ag/BiOX复合光催化剂具有更高催化活性的原因是复合光催化剂对可见光有很强的吸收能力,同时产生了银等离子体光催化作用和银抑制了Ag/BiOX(X=Cl,Br,I)的光生电子-空穴的复合.

Fabrication of a β-Bi_2O_3/BiOI heterojunction and its efficient photocatalysis for organic dye removal

To improve β-Bi2O3 photocatalysis,we couple β-Bi2O3 with BiO I to form β-Bi2O3/BiO I heterojunctions through an in-situ treatment with hydriodic acid. The prepared heterojunctions are characterized with X-ray diffraction,field emission scanning electron microscopy,transmission electron microscopy,ultra violet-diffuse reflectance spectroscopy,and X-ray photoelectron spectroscopy. Upon visible-light irradiation（λ 420 nm）,the β-Bi2O3/BiO I heterojunctions,especially with the molar ratio of HI to β-Bi2O3 at 0.4,exhibit much higher photocatalytic activity than pure β-Bi2O3 and BiO I for the degradation of methyl orange. The efficient separation of photogenerated electron-hole pairs across the interface of the heterojunction between β-Bi2O3 and BiO I would be responsible for the enhanced photocatalytic performances.

Improving hot corrosion resistance of aluminized TiAl alloy by anodization and pre-oxidation

To shield TiAl alloy from hot corrosion attack,a compact protective coating was fabricated by the combination of aluminizing,anodization and pre-oxidation.The hot corrosion behavior of the coated-TiAl specimen was investigated in the mixture salt consisting of 75 wt.%Na2SO4 and 25 wt.%NaCl at 700°C.Results indicated that the anodization and pre-oxidation were beneficial to the generation of Al2O3 layer,which could act as a diffusion barrier to prevent the molten salts and oxygen from diffusing into the alloy during exposure to a hot corrosion environment while the aluminizing coating could provide sufficient aluminum source to support the continuous formation of Al2O3 layer.Moreover,the internal stress of the coating was reduced due to the formation of a gradient coating consisting of TiAl3 and TiAl2.

Facile synthesis of hierarchical BiOCl_(x)Br_(1–x) solid solution with enhanced photocatalytic activity

The hierarchical BiOClxBr1–x was synthesized by a simple solvothermal method. The samples were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FESEM）, UV-visible diffuse reflectance spectroscopy （UV-vis DRS） and Brunauer-Emmett-Teller adsorption method. Compared to pure BiOCl or BiOBr, the BiOClxBr1–x solid solution has enhanced photocatalytic degradation activity for rhodamine B. This phenomenon can be explained to the hierarchical structure, lager specific surface area and appropriate energy gap of the obtained BiOClxBr1–x solid solution. The renewability and stability of photocatalyst were determinated and a possible mechanism of photocatalytic degradation was also proposed.

Pt/Bi_(24)O_(31)Cl_(10) composite nanosheets with significantly enhanced photocatalytic activity under visible light irradiation

Efficient composite semiconductor photocatalysts are highly desirable for the visible-light-driven degradation of organic pollutants. In this study, Bi24O31Cl10 photocatalyst was prepared via a hydrothermal method and modified with Pt nanoparticles (NPs) through a facile deposition procedure. The composite photocatalyst was characterized by X-ray diffraction, transmission electronic microscopy, X-ray photoelectron spectroscopy, UV-vis diffusion reflectance spectroscopy, photoluminescence spectroscopy, and electron spin resonance. The 1.0 wt% Pt/Bi24O31Cl10 photocatalyst showed the highest activity for the degradation of methyl orange under visible light (source: 300 W Xe lamp coupled with a UV-cutoff filter), and the photocatalytic degradation efficiency improved about 2.2 times compared to that of pure Bi24O31Cl10. The composite photocatalyst could maintain most of its activity after four runs of the photocatalytic experimental cycle. This study could provide a novel insight for the modification of other desirable semiconductor materials to achieve high photocatalytic activities.

分子前驱体煅烧法制备富铋催化剂及在油田废水处理中的应用

采用分子前驱体煅烧法制备卤化氧铋富铋催化剂,制备过程中用光降解罗丹明B实验探索煅烧时间和温度对催化剂活性的影响,从而优选出催化剂最佳制备条件。制备的Bi24O31Cl10、Bi24O31Br10、Bi5O7I光催化剂用X射线衍射仪、环境扫描电子显微镜,紫外可见漫反射分光光度仪以及光电流响应光谱进行表征分析其晶体结构、形貌以及光学性能。通过紫外可见光降解油田含酚废水来评价催化剂的活性,经过5 h的光降解作用后,Bi5O7I催化剂催化降解苯酚和双酚A的降解率分别为82.1%和78.1%。此法为制备富铋卤化氧铋催化剂提供一种新方向。

Ceria in halogen chemistry

Halogen chemistry constitutes an essential part in the industrial production of polymers and gains increasing attention as an attractive strategy to activate light alkanes that constitute natural gas. CeO2-based catalysts offer an exciting potential for advances in hydrogen halide recovery that enables a high efficiency of halogen-based processes for activation of small molecules. This review provides an overview of recently developed ceria-based catalysts in the context of polymer industry(polyvinyl chloride, polyurethanes, and polycarbonates) and activation of light hydrocarbons for natural gas upgrading. In addition, mechanistic insight and the challenges of ceria catalysts are provided, aiding the design of future catalytic materials and applications.

Synthesis,characterization,and activity of a covalently anchored heterogeneous perylene diimide photocatalyst

The consecutive two‐photon photocatalytic behavior of perylene diimide(PDI)enables it to catalyze photoreduction reactions that are thermodynamically unfavorable via single‐photon processes.In this work,we developed a heterogeneous PDI photocatalyst by covalently binding PDI molecules on the surface of nanosilica.This photocatalyst structure overcomes the intrinsic limitation of the low solubility of PDI,but retains its consecutive two‐photon photocatalytic property.Detailed characterization of the photocatalyst by techniques such as thermogravimetric analysis,solid‐state nuclear magnetic resonance spectroscopy,and Fourier transform infrared spectroscopy indicated that the PDI molecules were anchored covalently on the surface of nanosilica.The obtained photocatalyst reduced aryl halides under visible‐light irradiation in polar organic solvent and in water.The present study provides a promising strategy to realize two‐photon activity of PDI in common solvents for photocatalytic applications.

Delocalizedπ_(3)^(6) Bond in OX_(2) (X=Halogen) Molecules

OX_(2)(X=halogen)molecules was studied theoretically.Calculation results show that delocalizedπ_(3)^(6) bonds exist in their electronic structures and O atoms adopt the sp^(2) type of hybridization,which violates the prediction of the valence shell electron pair repulsion theory of sp^(3) type.Delocalization stabilization energy is proposed to measure the contribution of delocalizedπ_(3)^(6) bond to energy decrease and proves to bring extra-stability to the molecule.These phenomena can be summarized as a kind of coordinating effect.

Halogen adsorbates on polymer-stabilized gold clusters: Mass spectrometric detection and effects on catalysis

The mass spectrometry of gold clusters stabilized by poly（N‐vinyl‐2‐pyrrolidone） （Au：PVP） re‐vealed the presence of Cl adsorbates derived from synthetic precursors, mainly on the Au34 and Au43 clusters. Changes in the amount of Cl adsorbates on the Au clusters did not affect the catalytic prop‐erties for the aerobic oxidation of benzyl alcohol, suggesting that the Cl atoms were only weakly bound to the Au clusters. In contrast, the replacement of Cl with Br on the Au34 and Au43 clusters significantly suppressed activity, without any influence on the electronic structure. This result indi‐cated that the Br atoms were strongly bound to the Au clusters and sterically blocked their active sites. The substantial reduction of the catalytic activity by the Br adsorbates suggested that the Au34 and Au43 clusters made a major contribution to the catalytic activity of the Au：PVP.

Light-induced halogen defects as dynamic active sites for CO_(2) photoreduction to CO with 100%selectivity

Dynamic defects on halide perovskite materials,caused by ion dissociation and migration under light illumination,typically result in undesirable energy dissipation and limited energy conversion efficiency.However,in this work,we demonstrated that dynamic halogen defects generated by the same process in bismuth oxyhalide(Bi_(5)O_(7)Cl)materials can act as active sites to promote charge separation and photocatalytic efficiency.Mechanistic studies and density functional theory calculations revealed that dynamic Cl defects affected the electronic structure of Bi_(5)O_(7)Cl and photocatalytic CO_(2)reduction process.As active sites,these defects promoted charge transfer,leading to the activation of adsorbed CO_(2)molecules and reduction of the energy barrier of the rate-determining step.Thus,CO_(2)was spontaneously converted into COOH−intermediate and finally reduced to CO with a high efficiency of 108.60μmol g^(−1) and selectivity of 100%after 4-h of CO_(2)photoreduction.This work is highly instructive and valuable to the exploration of dynamic defects on halide-containing materials applied in solar energy conversion.

Surface composition-tunable octahedral PtCu nanoalloys advance the electrocatalytic performance on methanol and ethanol oxidation

The synthesis of surface composition-tunable Pt-based octahedral nanoalloys is key to unravel the structureproperty relationship in fuel cells. Herein, we report a facile route to prepare composition-tunable Pt Cu octahedral nanoalloys by using halogen ions(Br-or/and I-) as composition modulators. Among these Pt Cu octahedral nanoalloys,Pt59 Cu41 octahedron exhibits the highest catalytic activity and durability in alkaline solution. The specific activity/mass activity of Pt59 Cu41 octahedron is 20.25 m A cm^-2/3.24 A mg^-1 Pt,which is 6.64/5.3 times higher than commercial Pt black in 0.5 mol L^-1 CH3 OH, respectively. In the case of using ethanol(0.5 mol L^-1) as fuel source, Pt59 Cu41 octahedron shows much better catalytic activity, that is 34.84 m A cm^-2/5.58 A mg^-1 Pt for specific activity/mass activity, which is 9.16/7.34 times higher than commercial Pt black, respectively. In situ Fourier transform infrared spectroscopy is employed to detect the intermediate species and products for methanol/ethanol oxidation reaction and a plausible mechanism is proposed to explain the improved activity and durability of Pt59 Cu41 octahedron toward methanol/ethanol oxidation in alkaline medium.

Electrocatalytic water-splitting for the controllable and sustainable synthesis of deuterated chemicals

Tandem water electrolysis for the transformation of universal feedstock to value-added chemicals integrated with hydrogen generation and in situ utilization is a promising approach to address the economic challenges of electrochemical hydrogen evolution and storage.Herein,we present the controllable electrocatalytic deuteration of halides using inexpensive and reusable heavy water(D2 O)as a D-source for the preparation of valuable D-labelled chemicals and pharmaceuticals under mild conditions.This electrochemical deuteration method with high efficiency and selectivity furnishes a series of D-labelled chemicals and pharmaceuticals in high yields with excellent D-incorporation.The reaction efficiency and selectivity,that is,the precise substitution of deuterium atoms at different halogen positions,can be tuned by varying the applied voltages.The results show the great potential of green and economical electrocatalytic methods for producing value-added fine chemicals in addition to hydrogen evolution.

FeCl_3·6H_2O-catalyzed selective reduction of allylic halides to alkenes with concomitant oxidation of benzylic alcohols to aldehydes

Iron-catalyzed direct reduction of allylic halides with benzylic alcohol was achieved,providing a new,simple,and efficient method for conducting highly regioselective hydrodehalogenation.This method not only features a readily available reductant,an inexpensive catalyst,simple manipulation,and good tolerance of functional groups including nitriles,nitro,esters,and methoxyl groups,it also has mild reaction conditions and shows complete regioselectivity in that only halides sited at the allylic position are reduced.Alternatively,this method can be applied in the selective transformation of benzylic alcohols to aromatic aldehydes without overoxidation to carboxylic acids.