g-C3N4/Ag/TiO2复合材料的构筑及其光催化性能（英文）

以合成的g-C3N4纳米片和Ag/TiO2空心微球为原料,采用机械搅拌的方法构筑了g-C3N4/Ag/TiO2三元复合光催化剂。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、X射线光电子能谱(XPS)、紫外-可见光漫反射(UV-Vis DRS)和光致发光光谱(PL)对g-C3N4/Ag/TiO2进行了表征。研究表明,g-C3N4/Ag/TiO2是由Ag/TiO2微球和g-C3N4纳米片复合而成的。与TiO2相比,其可见光响应范围延长,光生载流子的分离速率加快。在室温下,用降解罗丹明B的反应考察了g-C3N4/Ag/TiO2的可见光催化活性。研究表明,光照180 min时,g-C3N4(0.5%)/Ag/TiO2显示了最高的光催化活性(91.9%),分别是TiO2和Ag/TiO2的7.5和1.8倍。光催化活性的提高与合理的异质结构建和Ag的导电性能有关。     

纳米复合材料Ag/MxOy-TiO2(MxOy=ZnO、Al2O3和Fe2O3)的制备及其微波辅助光催化降解甲基橙

采用溶胶-凝胶-程序升温溶剂热一步法,利用表面活性剂EO₂₀PO₇₀EO₂₀(P123)作为模板剂,分别制备了三元纳米复合材料Ag/ZnO-TiO₂、Ag/Al₂O₃-TiO₂和Ag/Fe₂O₃-TiO₂。通过XRD、氮气吸附-脱附测定、TEM以及扫描电子显微镜配合X-射线能量色散谱仪(SEM-EDS)等对合成的3种催化剂进行了对比表征分析。结果表明,复合材料Ag/M_xO_y-TiO₂中Ag以单质形式存在并较好地分布在M_xO_y-TiO₂表面上。所合成产物颗粒尺寸较小(约10 nm左右),形貌较好。其中,Ag/ZnO-TiO₂的比表面积与Ag/Al₂O₃-TiO₂十分相近,略大于Ag/Fe₂O₃-TiO₂。光催化活性研究中,以甲基橙为模型分子且辅以微波场作用。结果显示,上述三元复合材料的活性均明显高于未掺杂银的二元复合材料,其中Ag/ZnO-TiO₂的光催化活性最好,在90 min内对甲基橙的降解率高达86%。     

Low temperature synthesis of nanosized ZnNb<Subscript>2</Subscript>O<Subscript>6</Subscript> photocatalysts by a citrate complex method

Nanosized ZnNb₂O₆ photocatalysts (band gaps ~4.0 eV) were successfully synthesized via a citrate complex method. Their particle sizes ranged from 50 to 150 nm. The result of Mott–Schottky measurement revealed that the flat-band potential of ZnNb₂O₆ was ca. −1.3 V versus Ag/AgCl at pH 6.6. The photocatalytic activities of the samples for the degradation of methyl orange were evaluated under UV-light (λ = 254 nm). It was found that the sample obtained at 850 °C showed the highest photocatalytic activity due to its opportune crystallinity and surface area. Furthermore, ·OH radicals were detected as the major oxidation agents responsible for the decomposition of methyl orange.     

Activation of Au–Ag Plasmonic Bimetallic Nanocatalysts with Cold Plasma: The Role of Loading Sequence of Plasmonic Metals and Discharge Atmosphere

The activation of Au–Ag plasmonic bimetallic nanocatalyst can make the nanocatalyst exhibit superior visible-light (VL) photocatalytic activity. An efficient activation of Au–Ag nanocatalyst by cold plasma requires the restructuring of Au and Ag species over catalyst surface to form Au–Ag alloy nanoparticles while suppressing agglomeration of the nanoparticles. We here report that the loading sequence of Au and Ag components on titanium dioxide (TiO₂) support during catalyst preparation and discharge atmosphere play important roles in the plasma activation. Preparation of AuAg/TiO₂ nanocatalyst by depositing Ag and Au in sequence could avoid the undesired loss of Ag component, and ensure an effective restructuring of Au and Ag species in O₂ plasma activation. Compared with the reductive (H₂) and inert (Ar and N₂) plasmas, discharge in oxidative O₂ establishes Coulomb field with the negatively charged species over catalyst surface and enable the restructuring and intimate interaction of Au and Ag species. The catalyst characterization and density functional theory calculations suggest that O₂ plasma endows AuAg/TiO₂ nanocatalyst with large numbers of Au–Ag alloy nanoparticles, small size of plasmonic nanoparticles, high density of coordinatively unsaturated sites, and high content of surface oxygen species in the activation, which facilitates the adsorption and activation of O₂, and thus CO oxidation reaction under VL irradiation.

     

A new approach to the preparation of microcrystalline ZnNb2O6 photocatalysts via a water-soluble niobium-citrate-peroxo compound

A water-soluble niobium-citrate-peroxo compound was synthesized by using Nb₂O₅ as a precursor. This niobium compound solution was successfully applied to the preparation of microcrystalline ZnNb₂O₆ photocatalysts via a water-based sol-gel method. The results indicated that pure ZnNb₂O₆ could be obtained in a temperature range from 750 to 950 °C. The absorption edge of ZnNb₂O₆ located at about 305 nm, corresponding to a band gap of ca. 4.06 eV. The photocatalytic activities of the as-prepared samples for the methyl orange degradation were evaluated under UV light (λ = 254 nm). It was found that the sample obtained at 850 °C showed the highest photocatalytic activity due to its suitable surface area and crystallinity.     

Surface Plasmon Resonance‐Enhanced Visible‐NIR‐Driven Photocatalytic and Photothermal Catalytic Performance by Ag/Mesoporous Black TiO2 Nanotube Heterojunctions

Ag/mesoporous black TiO₂ nanotubes heterojunctions (Ag‐MBTHs) were fabricated through a surface hydrogenation, wet‐impregnation and photoreduction strategy. The as‐prepared Ag‐MBTHs possess a relatively high specific surface area of ≈85 m² g^?1 and an average pore size of ≈13.2 nm. The Ag‐MBTHs with a narrow band gap of ≈2.63 eV extend the photoresponse from UV to the visible‐light and near‐infrared (NIR) region. They exhibit excellent visible‐NIR‐driven photothermal catalytic and photocatalytic performance for complete conversion of nitro aromatic compounds (100 %) and mineralization of highly toxic phenol (100 %). The enhancement can be attributed to the mesoporous hollow structures increasing the light multi‐refraction, the Ti³⁺ in frameworks and the surface plasmon resonance (SPR) effect of plasmonic Ag nanoparticles favoring light‐harvesting and spatial separation of photogenerated electron–hole pairs, which is confirmed by transient fluorescence. The fabrication of this SPR‐enhanced visible‐NIR‐driven Ag‐MBTHs catalyst may provide new insights for designing other high‐performance heterojunctions as photocatalytic and photothermal catalytic nanomaterials.     

Effect of Ag doping concentration on the electronic and optical properties of anatase TiO2: a DFT-based theoretical study

The electronic and optical properties of pure and Ag-doped anatase TiO₂ have been calculated by spin-polarized density functional theory. Ag-doped TiO₂ with different Ag doping concentrations ranging from 2.08 to 8.33 % was investigated, and the electronic and optical properties evaluated. Substitutional Ag doped at Ti sites introduced Ag 4d states just above the valence-band maximum, which may help in shifting visible-light excited electrons to the conduction band. Our results show that increasing the doping concentration will enhance visible-light absorption up to Ag doping concentration of 6.25 %; however, further increase of the doping concentration leads to a decrease in visible-light absorption. These results indicate the possibility of tailoring the band gap and optical absorption of TiO₂ doped with Ag by varying the doping concentration. The enhanced visible-light absorption for Ag-doped TiO₂ with doping concentration of 6.25 % may be due to the existence of widely distributed Ag 4d states above the valence-band maximum and the optimal doping concentration. Ag doping shifted the absorption edge of TiO₂ towards visible light, consistent with recent experimental results. Our calculation results provide a reasonable explanation for the experimental findings.     

Visible-Light Activities of Erbium Doped BiVO4 Photocatalysts

Er-doped BiVO₄ composite photocatalyst was hydrothermal synthesized and characterizedby X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray Spectroscopy, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectra techniques. The activity of the catalyst was determined by oxidative decomposition of methyl orange in aqueous solution under visible-light irradiation. X-ray photoelectron spectroscopy and energy-dispersive X-ray Spectroscopy analysis revealed that the doped Er existed in the form of Er₂O₃. It also showed that the Er doping can enhance the visible-light absorption abilities of catalysts and their visible-light-driven photocatalytic activities in comparison with those of pure BiVO₄.     

Construction of 2D-2D TiO2 nanosheet/layered WS2 heterojunctions with enhanced visible-light-responsive photocatalytic activity

Constructing nanocomposites that combine the advantages of composite materials, nanomaterials, and interfaces has been regarded as an important strategy to improve the photocatalytic activity of TiO₂. In this study, 2D-2D TiO₂ nanosheet/layered WS₂ (TNS/WS₂) heterojunctions were prepared via a hydrothermal method. The structure and morphology of the photocatalysts were systematically characterized. Layered WS₂ (～4 layers) was wrapped on the surface of TiO₂ nanosheets with a plate-to-plate stacked structure and connected with each other by W=O bonds. The as-prepared TNS/WS₂ heterojunctions showed higher photocatalytic activity for the degradation of RhB under visible-light irradiation, than pristine TiO₂ nanosheets and layered WS₂. The improvement of photocatalytic activity was primarily attributed to enhanced charge separation efficiency, which originated from the perfect 2D-2D nanointerfaces and intimate interfacial contacts between TiO₂ nanosheets and layered WS₂. Based on experimental results, a double-transfer photocatalytic mechanism for the TNS/WS₂ heterojunctions was proposed and discussed. This work provides new insights for synthesizing highly efficient and environmentally stable photocatalysts by engineering the surface heterojunctions.     

Preparation of Ag deposited TiO2 (Ag/TiO2) composites and investigation on visible-light photocatalytic degradation activity in magnetic field

In this study, Ag deposited TiO₂ (Ag/TiO₂) composites were prepared by three different methods (Ultraviolet Irradiation Deposition (UID), Vitamin C Reduction (VCR) and Sodium Borohydride Reduction (SBR)) for the visible-light photocatalytic degradation of organic dyes in magnetic field. And then the prepared Ag deposited TiO₂ (Ag/TiO₂) composites were characterized physically by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The visible-light photocatalytic activities of these three kinds of Ag deposited TiO₂ (Ag/TiO₂) composites were examined and compared through the degradation of several organic dyes under visible-light irradiation in magnetic field. In addition, some influence factors such as visible-light irradiation time, organic dye concentration, revolution speed, magnetic field intensity and organic dye kind on the visible-light photocatalytic activity of Ag deposited TiO₂ (Ag/TiO₂) composite were reviewed. The research results showed that the presence of magnetic field significantly enhanced the visible-light photocatalytic activity of Ag deposited TiO₂ (Ag/TiO₂) composites and then contributed to the degradation of organic dyes.     

Disinfection of Escherichia Coli Gram Negative Bacteria Using Surface Modified TiO2: Optimization of Ag Metallization and Depiction of Charge Transfer Mechanism

The antibacterial activity of silver deposited TiO₂ (Ag‐TiO₂) against Gram negative Escherichia coli bacteria was investigated by varying the Ag metal content from 0.10 to 0.50% on the surface of TiO₂. Ag depositions by the photoreduction method were found to be stable. Surface silver metallization was confirmed by EDAX and XPS studies. Photoluminescence studies show that the charge carrier recombination is less for 0.1% Ag‐TiO₂ and this catalyst shows superior bactericidal activity under solar light irradiation compared to Sol gel TiO₂ (SG‐TiO₂) due to the surface plasmon effect. The energy levels of deposited Ag are dependent on the Ag content and it varies from ?4.64 eV to ?1.30 eV with respect to the vacuum energy level based on atomic silver to bulk silver deposits. The ability of electron transfer from Ag deposit to O₂ depends on the position of the energy levels. The 0.25% and 0.50% Ag depositions showed detrimental effect on bactericidal activity due to the mismatch of energy levels. The effect of the EROS (External generation of the Reactive Oxygen Species by 0.1% Ag‐TiO₂) and IROS (Interior generation of Reactive Oxygen Species within the bacteria) on the bactericidal inactivation is discussed in detail.     

Photocatalytic Oxidative Coupling of Methane over Au1Ag Single-Atom Alloy Modified ZnO with Oxygen and Water Vapor: Synergy of Gold and Silver

C−H dissociation and C−C coupling are two key steps in converting CH₄ into multi-carbon compounds. Here we report a synergy of Au and Ag to greatly promote C₂H₆ formation over Au₁Ag single-atom alloy nanoparticles (Au₁Ag NPs)-modified ZnO catalyst via photocatalytic oxidative coupling of methane (POCM) with O₂ and H₂O. Atomically dispersed Au in Au₁Ag NPs effectively promotes the dissociation of O₂ and H₂O into *OOH, promoting C−H activation of CH₄ on the photogenerated O⁻ to form *CH₃. Electron-deficient Au single atoms, as hopping ladders, also facilitate the migration of electron donor *CH₃ from ZnO to Au₁Ag NPs. Finally, *CH₃ coupling can readily occur on Ag atoms of Au₁Ag NPs. An excellent C₂H₆ yield of 14.0 mmol g⁻¹ h⁻¹ with a selectivity of 79 % and an apparent quantum yield of 14.6 % at 350 nm is obtained via POCM with O₂ and H₂O, which is at least two times that of the photocatalytic system. The bimetallic synergistic strategy offers guidance for future catalyst design for POCM with O₂ and H₂O.     

锡掺杂Bi2O3可见光响应光催化剂的制备及性能

以硝酸铋和四氯化锡为原料,采用浸渍法制备了纯Bi2O3和Sn掺杂Bi2O3光催化剂。利用X射线光电子能谱、X射线荧光光谱、X射线衍射、扫描电子显微镜、紫外-可见吸收光谱和光致发光光谱对样品进行了表征。在可见光下,利用2,4-二氯苯酚水溶液的光催化降解作为探针反应,考察了样品的可见光催化活性。结果表明,浸渍法能较好地实现Sn的掺杂,催化剂中掺杂剂Sn的价态为+4价,以锡的氧化物形式存在于Bi2O3晶格间隙或晶粒表面。并且掺杂适量的Sn,可有效抑制Bi2O3晶相由四方相向单斜相的转变,拓宽了Bi2O3的可见光响应范围,有效阻止了光生电子和空穴的复合,从而提高了Bi2O3的可见光催化活性。当Sn的掺杂量为2%时(物质的量的分数),Bi2O3具有最好的可见光催化活性。     

Cu3B2O6/CuB2O4单晶的制备及其可见光催化降解亚甲基蓝

以醋酸铜/硝酸铜和硼酸为原料,柠檬酸作发泡剂,采用溶胶-凝胶法制得了高纯度的单晶结构硼酸铜（Cu₃B₂O₆/CuB₂O₄）. 利用X射线衍射（XRD）、扫描电镜（SEM）、高分辨率透射电镜（HRTEM）、热重-差热分析（TGDTA）等对样品进行了表征,并考察了Cu₃B₂O₆/CuB₂O₄在可见光（400 nm<λ<1100 nm）下对亚甲基蓝（MB）溶液的催化降解性能. 结果表明,两种结构的硼酸铜都具有良好的光催化性能. 当亚甲基蓝的初始浓度为50 mg·L^-1,催化剂用量为1 g·L^-1,光照6 h后,CuB₂O₄对亚甲基蓝的光催化降解率为63.36%,Cu₃B₂O₆对亚甲基蓝的光催化降解率为99.52%. 紫外-可见漫反射光谱（UV-Vis DRS）结果表明,Cu₃B₂O₆的中间能态宽度为1.78 eV,小于CuB₂O₄的中间能态宽度（1.95 eV）,且Cu₃B₂O₆的禁带宽度较窄（E_g=2.34 eV）,不仅可以发生价带顶与中间能态的电子跃迁,同时可以发生禁带间的电子跃迁,所以Cu₃B₂O₆比CuB₂O₄具有更高的可见光催化性能.     

Degradation of terbuthylazine by Fe/TiO2 with visible-light-driven photo-Fenton catalytic activity

In order to improve the catalytic activity of Fenton catalyst, a composite catalyst, Fe/TiO₂, with both visible-light photocatalytic and Fenton-like catalytic activities was synthesized via a brief solvothermal process. The XRD and SEM results indicated that Fe was dispersed homogeneously on the surface of TiO₂ in the form of Fe₂O₃, and the loading of Fe did not have significant effects on the particle size and morphology of TiO₂. The EDS results showed that the loading content of Fe was about 1.4 wt%. The photocatalytic results showed that the prepared Fe/TiO₂ composite catalyst had excellent catalytic behaviors for terbuthylazine degradation under visible-irradiation with H₂O₂ assistance, the degradation ratio reached up to 90% after 120 min. The reinforced degradation performance were primarily attributable to the introduction of carrier TiO₂, which expanded visible response range by H₂O₂ adsorption, and accelerated the cycle of Fe (Ⅱ)/Fe (Ⅲ). The fluorescent spectroscopy results revealed that the degradation process of terbuthylazine involved the generation and participation of active species such as hydroxyl radicals and superoxide radicals. This study is expected to provide a visual approach for designing a novel photo-Fenton catalyst to jointly utilize both photocatalytic and Fenton activities, which can be better applied to the actual use of organics purification in wastewater.     

S掺杂的HTiNbO5纳米片: 一种新型高效可见光催化剂

将层状HTiNbO₅剥层絮凝成HTiNbO₅纳米片, 然后与硫脲焙烧, 制得了S掺杂的HTiNbO₅纳米片. 与原始HTiNbO₅和HTiNbO₅纳米片相比, 该样品具有较大的比表面积和明显的可见光吸收. 以罗丹明B为降解物, 评价了该催化剂的吸附性能和可见光催化性能. 结果表明, HTiNbO₅纳米片和S掺杂的HTiNbO₅纳米片都具有很好的吸附能力和很高的可见光降解速率. 然而, 对于罗丹明B的矿化, S掺杂的HTiNbO₅纳米片可以达到41%矿化率, 而HTiNbO₅纳米片上矿化单几乎为零. 这说明S掺杂能有效改善纳米片的光催化效果. 最后, 对可能的光催化机理进行了探讨.     

Green synthesis and characterization of Ag and Ag/Fe3O4 nanocomposites for antimicrobial effect and rhodamine- B dye degradation

We used a simple two-stage tactic to design and synthesize a magnetically separable catalyst (MSC) Ag/Fe₃O₄ by combining independently synthesized Fe₃O₄ and Jatropha curcas root functionalized Ag nanoparticles (NPs) at room temperature. The phase composition of Ag/Fe₃O₄ NCs was revealed by morphological and structural assessment. The derived Ag/Fe₃O₄ nanocomposites demonstrated outstanding antimicrobial activity against Gram-negative Pseudomonas aeruginosa comparing to Gram-positive Bacillus subtilis which was determined by the agar well diffusion method. This is due to positively charged surface of metal oxide NPs that may bind to cell membrane. Interestingly, Ag–Fe₃O₄ NCs demonstrated good photocatalytic activity for organic dye degradation. According to a kinetic study, Ag/Fe₃O₄ MSC removed 99% of Rhodamine B at a rate constant of 1.89 min^?1. The photoelectron could perhaps ultimately collide only with dissolved solids in the substrate to form superoxides, which can damage the dye. Notably, the MSCs reusability was tested using magnetic detachment without sacrificing photocatalytic efficiency. This finding represents a significant breakthrough in the domain of wastewater treatment and biomedicine.     

可见光辐射下活性炭-铁酸镍杂化催化剂光催化氧化氨氮

铁酸镍（NiFe₂O₄）中的镍原子抑制其光芬顿催化活性. 然而,活性炭（AC）能激活其光芬顿催化活性,结果导致复合催化剂AC-NiFe₂O₄在过氧化氢存在时可见光辐射下也可催化氧化氨氮. 用X射线衍射（XRD）,透射电镜（TEM）,傅里叶变换红外（FTIR）光谱,紫外-可见漫反射光谱（UV-Vis DRS）,比表面积和振动样品磁强计对催化剂进行了表征. 光催化降解氨氮的实验表明,该复合催化剂在10 h内氨氮的降解率可达到91.0%,而同样条件下没有催化剂时氨氮的去除率只有24.0%. 对照实验表明,裸铁酸镍在可见光辐射下,氨氮的降解率只有30.0%. 这表明活性炭加速了氨氮的氧化速率. 动力学研究表明,氨氮的氧化遵循一级反应动力学规律,其表观反应动力学常数为3.538×10^-3 min^-1. 机理研究表明,氨氮的氧化是通过生成HONH₂ 中间体,然后转化为NO₂^- .8次循环实验表明该复合催化剂容易分离、可循环使用、且催化活性十分稳定. 因此,该催化剂具有潜在的应用价值.     

Hydrogenation and Ammoniation of SrTiO3 for an Enhanced Visible-light Photocatalysis

Hydrogenation and ammoniation of SrTiO₃ (STO), a normal ultraviolet photocatalyst, were performed by annealing STO〈100〉in H₂:N₂=5%:95% and NH₃, respectively, at various tem-peratures T. It was found that hydrogenation at T≥900 oC remarkably enhanced the UV photocatalytic ability of STO, but the visible-light photocatalysis was still unavailable, while ammoniation at T≥800 oC introduced the N doping, resulting in visible-light photocat-alytic activity. Furthermore, when a hydrogenated STO was subjected to ammoniation, the visible-light photocatalytic ability was nearly the same as that of the ammoniated one; but the hydrogenation of an ammoniated one significantly enhanced visible-light photocatalysis, indicating a synergetic effect of hydrogenation and ammoniation. Discussions and identifi-cations have been made to analyze these results.     

利用AgVO3改性MoS2增强活性氧产生及其光催化性能的提高

随着全球工业化进程的发展,环境污染问题日益严重,已经成为21世纪影响人类生存与发展的重要问题.光催化氧化技术被认为是解决环境问题最有应用前景的技术之一,已经成为环境领域的研究热点.众所周知,二硫化钼(MoS2)可以被可见光激发产生电子-空穴对,但是由于其氧化还原电势并不高,抑制了氧分子活化的量子效率,且激发后的光生载流子容易复合,导致光催化效率不高.因此,迫切需要对MoS2光催化材料进行修饰与改性,采用提高光催化过程中活性氧(ROSs)的量来提高其光催化活性.银钒氧化物(AgVO3,Ag2V4O11,Ag3VO4和Ag4V2O7等)因其在锂电池、传感器和光催化剂领域的应用而引起了人们的关注.其中,AgVO3具有较窄的带隙和高度分散的价带,具有潜在的应用价值.本文采用水热法成功制备了AgVO3/MoS2复合光催化剂,并采用X射线粉末衍射、扫描电子显微、透射电子显微镜和紫外-可见漫反射光谱等表征技术研究了所制光催化剂的物相结构、样品形貌和光学性能.以四环素为研究对象,将其应用于AgVO3/MoS2复合光催化剂的降解实验.结果表明,随着AgVO3质量比从1.0 wt%增加到3.0 wt%,所得催化剂的光催化活性不断提高;当进一步增加AgVO3的质量时,复合催化剂的活性逐渐降低.这是由于过多的AgVO3的引入导致在光催化剂表面形成电子-空穴对复合中心,增加了载流子复合几率.因此,AgVO3/MoS2复合光催化剂中AgVO3的最佳质量比为3.0 wt%,其降解速率常数为0.0087 min–1,分别是MoS2(0.00509 min–1)和AgVO3(0.00495 min–1)的1.71和1.76倍.由于AgVO3改性后的MoS2具有优异的光催化性能,能促进O2的吸附/活化,加速MoS2表面生成H2O2的双电子氧还原反应,从而产生更多的ROSs.利用电子自旋共振光谱、POPHA荧光检测和自由基捕获实验相结合的方法来阐明ROSs的形成机理.同时,ROSs的产生会加速消耗AgOV3导带上的电子,为降解污染物留下更多的空穴.本文为表面催化工程促进ROSs生成的合理设计提供了新的思路,有望在环境治理中得到实际应用.