分级微球BiOBr和BiOI的制备及光催化活性比较

以五水硝酸铋、溴化钠和碘化钾为原料,乙二醇为溶剂,采用一步溶剂热法制备了分级结构微球BiOBr和BiOI。比较了两种催化剂在可见光和模拟日光下对罗丹明B的降解效果。结果表明,在模拟日光和可见光下,BiOBr的催化活性要好于BiOI,同时对机理进行了深入探讨。     

Facile one-pot synthesis of a BiOBr/Bi2WO6 heterojunction with enhanced visible-light photocatalytic activity for tetracycline degradation

Photocatalytic removal of tetracycline (TC) from the wastewater is of great value in the chemical and environmental engineering field. Here, we introduced a facile one-step method for the synthesis of BiOBr/Bi₂WO₆ heterojunctions by using cheap CTAB as the Br source. We showed the possibility of our method to fine-tune the content of BiOBr in the produced BiOBr/Bi₂WO₆ by simply changing the dosage of cetyltrimethylammonium bromide (CTAB), providing a platform for the delicate tuning of the visible-light absorbance ability of the composites. With a suitable heterojunction structure of BiOBr/Bi₂WO₆-0.2, it exhibited an ultrarapid photocatalytic activity towards TC (20 mg·L^-1), with a competitive removal efficiency of 88.1% within 60 min and an ultrahigh removal rate of 0.0349 min^-1. It could also be robustly recycled for at least 5 cycles with slight removal efficiency loss. We demonstrated that this exciting photocatalytic performance was due to the highly decreased recombination of photoinduced electrons and holes on our composites by constructing this heterojunction structure, and the resulting OH and contributed to the effective degradation of TC to CO₂.     

溶剂热合成多级ZnO微球及其光催化降解苯酚

以乙二醇为溶剂,KAc为助剂,采用溶剂热法合成多级ZnO微球。通过改变反应温度来调控ZnO微球形貌,并对合成的ZnO微球进行XRD、SEM、PL和UV-Vis DRS等表征分析。结果表明,合成的ZnO为六方纤锌矿晶体结构,由短纳米棒自组装成多级微球。在紫外-可见光照射下,ZnO表现出优异的光催化降解苯酚活性,180℃合成的ZnO样品光催化活性明显优于其他温度合成的样品。用0.1 g的ZnO降解100 mL浓度为5 mg·L^(-1)的苯酚溶液,光照150 min降解率达94.5%。多级ZnO微球光催化性能的提高可推测为较窄的禁带宽度(3.08 eV)有利于吸收光子,较小的晶粒尺寸(25.38 nm)、粗糙的表面以及中空结构有利于反应液与催化剂表面的充分接触。此外,由捕获实验证实光催化降解苯酚的机理是羟基(·OH)为主要的活性自由基,在苯酚降解过程中起主要作用。     

Reduced graphene oxide as co-catalyst for enhanced visible light photocatalytic activity of BiOBr

BiOBr-reduced graphene oxide (RGO) composites were successfully synthesized via a simple hydrothermal method. Their morphology, structure and photocatalytic activity in the degradation of nitrobenzene were characterized by scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption, UV–vis absorption spectroscopy, photoluminescence spectra, electrochemical impedance spectra and total organic carbon, respectively. The results showed that the introduction of RGO could enhance the visible light photocatalytic activity of BiOBr. The BiOBr-RGO composite with 0.6 wt% RGO exhibited an optimal photocatalytic activity, and the maximum degradation rate of nitrobenzene was about 2.16 times that of pure BiOBr due to the increased light absorption and the reduced electron-hole pair recombination in BiOBr with the introduction of RGO.     

蒙脱石负载BiOI/BiOBr的合成及光催化降解罗丹明B

以硝酸铋、碘化钾和十六烷基三甲基溴化铵(CTAB)为原料,钙基蒙脱石为载体采用水热法合成了具有可见光响应的蒙脱石负载型BiOI/BiOBr异质结光催化剂。采用SEM、XRD、FT-IR、UV-Vis DRS等表征方法对其组成、晶型、形貌和光学吸收性能进行了研究。以有机染料罗丹明B(RhB)为目标降解物,考察了合成的负载型异质结催化剂的光催化活性,并初步探讨了其光催化性能提高的机理。     

离子液体辅助合成CdMoO_4微球体及其光催化性能

分别以1 mL 1-正丁基-3-甲基咪唑氯盐([Bmim]Cl)(离子液体Ⅰ)和1 mL 14,-双(N-甲基咪唑)丁烷溴盐([C4(Mim)2][Br]2)(离子液体Ⅱ)为辅助剂,CdCl2与Na2MoO4在60℃下反应1 h制备了单分散性较好的圆球状和椭球状的CdMoO4,并利用X射线衍射仪、扫描电子显微镜对产物的组成和形貌进行了表征。结果表明,在2种条件下制备的产物均为四方晶相的CdMoO4,但其大小有所差异。以紫外光灯为光源,2种不同离子液体合成的CdMoO4微球为光催化剂,对有机染料罗丹明B进行了光降解实验。研究发现,利用双阳离子液体合成的CdMoO4微椭球具有更高的光催化活性,经过60 min其光降解率达到了98.9%。     

Development of photocatalytic efficient Ti-based nanotubes and nanoribbons by conventional and microwave assisted synthesis strategies

Titanate nanotubes were prepared via a hydrothermal treatment of TiO₂ powders (Riedel De Haen) in a basic solution. Morphology and structure of the prepared samples were characterized by high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), XRD, FT-Raman spectroscopy, nitrogen sorption and DSC. The photocatalytic activity was evaluated by photocatalytic oxidation of rhodamine 6G. Trititanate nanotubes (TTNT) with inner pore diameters between 4 and 4.2 nm and surface areas up till 360 m²/g could be synthesized. The synthesis route was modified by introduction of a calcination step, by applying a lower hydrothermal temperature and microwave irradiation in order to increase the photocatalytic activity of the porous photoactive nanotubular materials. Calcination and a softer hydrothermal treatment led to the formation of anatase without affecting the surface area and nanotubular shape of the samples. In this way, the photocatalytic activity of the original trititanate nanotubes could be significantly increased. By making use of microwave assisted synthesis, the photocatalytic activity can also be increased due to the presence of anatase. However, by applying microwave synthesis, a different structure was obtained, nanoribbons (NR) instead of nanotubes, resulting in a decrease in surface area and porosity.     

Synthesis of multi-shelled ZnO hollow microspheres and their improved photocatalytic activity

Herein, we report an effective, facile, and low-cost route for preparing ZnO hollow microspheres with a controlled number of shells composed of small ZnO nanoparticles. The formation mechanism of multiple-shelled structures was investigated in detail. The number of shells is manipulated by using different diameters of carbonaceous microspheres. The products were characterized by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The as-prepared ZnO hollow microspheres and ZnO nanoparticles were then used to study the degradation of methyl orange (MO) dye under ultraviolet (UV) light irradiation, and the triple-shelled ZnO hollow microspheres exhibit the best photocatalytic activity. This work is helpful to develop ZnO-based photocatalysts with high photocatalytic performance in addressing environmental protection issues, and it is also anticipated to other multiple-shelled metal oxide hollow microsphere structures.     

In situ synthesis and enhanced visible light photocatalytic activity of C-TiO2 microspheres/carbon quantum dots

TiO₂ microspheres and TiO₂/carbon quantum dots (CQDs) composites with different CQDs contents were successfully synthesized via solvothermal and in situ hydrothermal method. The structure and morphology of the prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM). Results showed that carbon elements were successfully doped into the TiO₂ lattice (C-TiO₂) and CQDs were hybrid with C-TiO₂ microspheres. The X-ray photoelectron spectroscope (XPS), valence band XPS (VB-XPS) and UV–vis diffuse reflectance spectra (DRS) analyses revealed that carbon doped into TiO₂ microspheres could lead to local energy levels in the band structure and generate valence band tails to absorb visible light. The photocatalytic activities of these samples were evaluated by the photodegradation of Rhodamine B (RhB) under visible light irradiation. C-TiO₂/CQDs samples presented an enhanced photocatalytic performance compared with pristine TiO₂, which could be attributed to the present of CQDs, acting as adsorption sites for RhB molecules and charge separation centers to impede the recombination and prolong the life time of electron and hole pairs.     

光催化材料Bi4O7/BiOBr的制备及其光催化性能研究

以自制的铋酸钾（KBiO₃）为前驱物,采用低温水热法制备七氧化四铋（Bi₄O₇）,再利用氢溴酸原位离子刻蚀法首次成功制备了Bi₄O₇/BiOBr复合物。通过X射线衍射（XRD）和扫描电子显微镜（SEM）分别观测了样品的物相和形貌特征,复合相具有比二者单相更佳的可见光降解罗丹明B（RhB）的性能,最高可达到30 min内降解86.9%;紫外可见漫反射光谱（DRS）和光致发光光谱（PL）分别证明了其性能的提升是由于复合相拥有更广的光学响应范围和更低的光生载流子复合效率。超氧自由基和空穴是该体系光催化降解过程中的活性物质,并由此提出了一种可能的光催化降解机制,且复合相比单相Bi₄O₇具有更好的光催化降解稳定性。     

Morphology-controlled synthesis of CdSe microspheres on graphene oxide sheets and their photocatalytic properties

Different morphologies of CdSe microspheres have been synthesized on reduced graphene oxide (rGO) sheets by a simple hydrothermal process using Cadmium nitrate and Se powder as the raw materials. The hybrid CdSe/rGO samples were intensively investigated by XRD, EDS, XPS, SEM and UV–vis absorption spectrum. It was found that the EDTA/Cd²⁺ molar ratio is crucial for the formation of morphology of CdSe grown on rGO sheets. The results of XRD reveal that the as-prepared CdSe microspheres have zinc blend structure. The results of Raman spectra, EDS, XPS and SEM show that the CdSe microspheres are grown on rGO sheets. In addition, UV–vis absorption spectrum indicates that the CdSe/rGO nanocomposites are believed to serve as photosensitizers to extend the absorption spectrum to visible light region. Superior photocatalytic activity of urchin-like CdSe microspheres grown on rGO sheets relative to those of other CdSe/rGO nanocomposites was observed under visible light irradiation. The growth mechanism for the formation of CdSe microspheres grown on rGO sheets was also described.     

Fluoride-mediately solvothermal synthesis and tunable photocatalytic selectivity of urchin-like ZrO2 hollow microspheres

Photocatalysts often show excellent performances on the basis of their surface state of exposed faces with high reactivity, but unfortunately surfaces of this type are usually concealed into the interior of crystals for their high surface energy. We report here a possibility that for fluorine-terminated surfaces of monoclinic ZrO₂, these higher-energy surfaces could be retained and exposed. Urchin-like ZrO₂ hollow microspheres (UZHS) composed of nanoribbons with exposed (010) facets are obtained through a fluoride mediately solvothermal method. We prove the stabilization effect of fluorine adsorption on (010) facets by density functional theory calculations. More interestingly, UZHS exhibit tunable photocatalytic selectivity in dye degradation. The fluorinated UZHS exhibit good performances both on decomposing Congo red (CR) and methylene blue, while the surface-modified UZHS by calcination only favor decomposition of CR.     

Synthesis of thermally stable mesoporous TiO2 and investigation of its photocatalytic activity

The effects of heat treatment, dopant type and thickness of sol layer, on the formation and stability of ordered TiO₂ mesostructure were investigated. Higher ageing temperature facilitates the separation of organic phase and inorganic phase, while thinner sol layer facilitates the formation of homogeneous system and improves the mesostructural order of TiO₂. Lanthanum dopant, which is more electropositive than Ti, can improve the thermal stability of mesostructure by enhancing the strength of Ti–O bond. On the contrary, Fe and Pd dopants, which are more electronegative than Ti, decrease the thermal stability of mesostructure. Furthermore, La doped mesoporous TiO₂ shows high activity in the photocatalytic degradation of Rhodamine B under the irradiation of visible light.     

Synthesis of TiO2 microspheres by ultrasonic spray pyrolysis and photocatalytic activity evaluation

This work presents and discusses TiO₂ microspheres synthesized by ultrasonic spray pyrolysis. A simple setup allowed for the continuous production of TiO₂ nanocrystals. During the process, the particles experienced a short residence time (ca. 40 s) at the set temperature (700 °C), promoting phase stability and limited particle coarsening. As a result, porous anatase TiO₂ microspheres with crystallite size ～8 nm and specific surface area ～27 m² g^-1 were produced as soft spherical agglomerates of ～0.6 μm. Samples were analyzed using X-ray diffraction, BET specific surface area, SEM, TEM, XPS, and UV/Vis diffuse reflectance spectra, as well as in their photocatalytic activities. Photoactivity was evaluated through the degradation of the model contaminant acetaminophen under UV irradiation, and the results confirmed the superior performance of the synthesized TiO₂ microspheres, exceeding the commercial standard TiO₂ P25 by ca. 60% in terms of reactivity.     

Synthesis, structural characterization and photocatalytic activity of Ti-MCM-41 mesoporous molecular sieves

This paper reports the applicability of hydrothermal synthesis in alkaline medium for preparation of Ti-containing mesoporous MCM-41 materials. The influence of different parameters was investigated, such as the Ti source, the molar ratio between Si and Ti and also the synthesis temperature. Structural analysis shows that the high specific surface area, large pore size and well ordered mesostructure, are partially retained in the titania containing materials. Modifying synthesis temperature, it was shown that MCM-41 isotherms are different for temperatures above or under 140°C. UV-VisDR spectroscopy was used to investigate the local environment of Ti sites. The obtained materials were evaluated for the photocatalytic degradation of Rhodamine 6G in aqueous medium. The best photocatalytic activity was found for the sample prepared at higher ageing temperature of 160°C, at which anatase particles were formed.     

Facile synthesis of silica/polymer hybrid microspheres and hollow polymer microspheres

Monodisperse silica/polydivinylbenzene (SiO₂/PDVB) and silica/poly(ethyleneglycol dimethacrylate) (SiO₂/PEGDMA) core-shell hybrid microspheres were prepared by a two-stage reaction with silica particles' grafting of 3-(methacryloxy)propyltrimethoxysilane (MPS) as core and PDVB or PEGDMA as shell, in which the MPS-modified silica core with diameter of 238 nm was synthesized by Stöber method and subsequently grafted with MPS as the first-stage reaction. The PDVB or PEGDMA shell was then encapsulated over the MPS-modified silica core by distillation precipitation polymerization of divinylbenzene (DVB) or ethyleneglycol dimethacrylate (EGDMA) in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) initiator as the second-stage reaction. The encapsulation of PDVB and PEGDMA on modified silica core particles was driven by the capture of DVB or EGDMA oligomer radicals via the vinyl groups on the surface of the modified silica cores during the second-stage polymerization in the absence of any stabilizer or surfactant. The shell thickness of the core-shell hybrid particles was controlled by the feed of DVB or EGDMA monomer during the polymerization. Hollow PDVB or PEGDMA microspheres with various shell thickness were further developed after selective removal of the modified silica cores with hydrofluoric acid. The resultant core-shell hybrid materials and hollow microspheres were characterized by transmission electron microscopy (TEM), and Fourier transform infrared spectra (FT-IR).     

可见光驱动溴化银/溴氧化铋复合纳米 材料制备及活性评价*

室温沉淀法合成溴氧化铋（BiOBr）纳米片,然后通过离子交换法制备溴化银/溴氧化铋（AgBr/BiOBr）复合纳米材料,采用X射线衍射（XRD）、场发射扫描电子显微镜（FE-SEM）及紫外可见分光光度计（UV-Vis）对其进行表征,并进行了光催化降解实验。以节能、绿色的LED灯为可见光光源,AgBr/BiOBr复合材料光催化降解罗丹明B（RhB）和甲基橙（MO）的效率均高于BiOBr。AgBr/BiOBr降解RhB的活性强于MO。在AgBr/BiOBr光催化系统中,超氧自由基和空穴是主要的活性物种。不同pH条件下,AgBr/BiOBr对RhB均表现出理想的光催化降解效果,酸性条件下降解效率最佳;碱性环境下AgBr/BiOBr光催化降解MO的活性最高。经过循环利用,AgBr/BiOBr可见光催化活性呈现出一定程度的降低,归因于降解过程中产生了金属银。     

新型BiOBr光催化剂的制备及性能研究

采用水热合成法制备BiOBr可见光催化剂,选择适合的溴源,考察了水热反应温度和时间对制备催化剂的影响。同时采用XRD、BET、Uv-vis紫外-可见光谱等手段对样品进行了表征。研究了BiO-Br可见光照射下的光催化活性。结果表明,在水热反应温度为160℃、水热反应时间为8h的条件下,制备的BiOBr纳米材料具有很好的光催化活性,在降解罗丹明B染料时降解率达93%,BiOBr的晶型结构受反应条件的影响,它的禁带宽度为2.69eV。     

Synthesis of a CoTiO3/BiOBr heterojunction composite with enhanced photocatalytic performance

A novel heterojunction CoTiO₃/BiOBr nanocomposite with enhanced photocatalytic performance was synthesized by a precipitation-deposition method. The samples were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis spectrophotometry. Moreover, the photocatalytic activities were evaluated by decomposing the dye molecule Rhodamine B under visible light irradiation. The results showed that high photocatalytic performance can be achieved on the heterojunction photocatalysts, with the 0.15CoTiO₃/0.85BiOBr composite displaying the highest activity. The results of the study concluded that it was the introduction of CoTiO₃ into the catalyst that mainly enhanced the activity of the photocatalyst by promoting the separation of the electron-hole group on the interface between BiOBr and CoTiO₃.