基于表面等离子体共振效应的Ag(Au)/半导体纳米复合光催化剂的研究进展

由具有表面等离子体共振(surface plasmon resonance,SPR)效应的贵金属(Ag、Au等)纳米粒子和半导体纳米结构组成的纳米复合光催化剂具有优异的可见光光催化活性,成为新型光催化材料的研究热点之一。本文综述了Ag(Au)/半导体纳米复合光催化剂的制备方法、基本性质以及光催化应用方面的一些重要研究进展;重点介绍了Ag(Au)等纳米粒子的表面等离子共振增强可见光催化活性的机理,以及Ag(Au)纳米粒子与不同类型半导体复合的光催化剂的光催化性能,其中所涉及的半导体包括金属氧化物、硫化物和其他一些半导体;本领域未来几年的研究热点将集中于新型高效的Ag(Au)/半导体纳米复合光催化剂的微结构调控及其用于可见光驱动有机反应的机理研究。本文为基于SPR效应构建Ag(Au)/半导体纳米复合光催化剂的研究提供了有力的参考依据,并且指出Ag(Au)/半导体纳米复合光催化剂的研究是发展可见光高效光催化剂的重要方向。     

纳米ZnO/膨润土光催化降解亚甲基蓝研究

以Zn(NO3)2和膨润土为原料,采用沉淀法制备纳米ZnO-膨润土复合光催化材料,用FT-IR、XRD和SEM对其结构和形貌进行了表征。以高压汞灯为光源,光催化降解活性亚甲基蓝模拟染料废水,研究了ZnO/有机膨润土光催化降解性能,讨论了影响亚甲基蓝降解率主要因素。结果表明,在光照射下1.5 h,ZnO/膨润土光催化降解亚甲基蓝达96%,其重复使用降解效果保持稳定,利用该复合光催化材料降解有机染料废水是一种可行的方法。     

硫化物光催化剂的形貌控制及光催化性能的研究进展

无机纳米材料的结构、维度、形貌、尺寸等因素对它们的功能性能有着直接影响。CdS、ZnS以及其复合纳米材料在光、电、磁、催化和力学等方面有着特殊的性能,这与晶体形态和形貌紧密相关,因此制备可控粒度、形状、取向的CdS等硫化物半导体纳米材料,研究其结构、形貌对光催化性能的影响,对新型高效光催化材料的研究与开发具有重要的意义。本文重点介绍了近几年硫化物形貌和粒径的控制的研究进展以及此类光催化剂在光催化分解水制氢和降解有机染料等方面的应用。     

Effect of surfactant in a modified sol on the physicochemical properties and photocatalytic activity of crystalline TiO<Subscript>2</Subscript> nanoparticles

This study describes the effect of amphiphilic organic molecules (surfactants) in a sol on the physicochemical properties and photocatalytic activity of crystalline TiO₂ nanoparticles prepared via a simple sol–gel route at high temperatures from 400 to 800 °C. Addition of polyoxyethylenesorbitan surfactant and polyethylene oxide and polypropylene oxide triblock copolymer as particle size inhibitors and pore directing agents into a stable titania sol affected the physicochemical properties of TiO₂ nanoparticles such as their crystallographic structure, morphology, and defect structure. With the addition of the surfactants, the ratio of anatase and rutile crystal phases of TiO₂ was controlled and an active anatase crystal phase was maintained during heat treatment up to 800 °C. Decrease in the sintering rate and inhibition in crystal growth were also observed, which resulted in higher surface area and inhibition of crystallite aggregation. Bulk defects in TiO₂ were reduced while surface defects were increased as a result of the addition of surfactants. These physicochemical properties of TiO₂ nanoparticles were correlated with photocatalytic degradation of 4-chlorophenol in water. The results revealed that high crystallinity, anatase crystal phase, high specific surface area, surface defects, and segregated morphology of TiO₂ nanoparticles, which were induced by the addition of surfactants, were more advantageous for enhancing photocatalytic destruction of the model organic compound tested in the study.     

磷酸银光催化性能提升与增强机制的研究进展

Ag₃PO₄是目前光催化效率最高的可见光光催化剂之一,在降解有机污染物、分解水制氢和CO₂还原等领域具有广泛的应用前景。但Ag₃PO₄光催化性能距离实际应用还存在一定差距,化学性质也不稳定,因此对其性能提升受到了各国研究者的关注。围绕Ag₃PO₄纳米化、形貌控制、异质结构等提升光催化性能的途径及其增强机制进行阐述,其中与Ag₃PO₄形成异质结构是目前提升其光催化性能的最主流的方法,Ag₃PO₄与金属氧化物、卤化物、硫化物、有机半导体、单质金属形成的异质结构均有效改善了其光催化性能,最后还对Ag₃PO₄基光催化剂未来的发展趋势进行了展望。     

溶胶-凝胶-微波法制备银掺杂TiO_2光催化剂及其光催化性能

用硝酸银和钛酸正丁酯为原料,采用溶胶-凝胶-微波辐射干燥法合成银掺杂TiO_2光催化剂TiO_2-Ag。为了提高催化剂的光催化活性和降解有机污染物的速率,用微波辅助Ti O2-Ag光催化剂降解有机污染物。通过扫描电子显微镜、红外光谱法、紫外可见光谱法和荧光光谱法对TiO_2-Ag催化剂进行测试和表征。以甲基橙为有机污染物,分别在太阳光照射和微波、紫外、紫外-微波条件下降解甲基橙以考察催化剂的光催化活性。结果表明,TiO_2-Ag光催化剂最佳制备条件为:银掺杂量n(Ag+)∶n(Ti~(4+))=0.003,离子液体用量3.0 m L,微波干燥功率210 W,微波干燥时间20 min,焙烧温度650℃,焙烧时间3 h,此条件下制备的TiO_2-Ag光催化剂在太阳光照射4 h下,紫外光照、微波辐射和紫外光照-微波辐射分别辐射55 min后,甲基橙降解率分别为98.70%、98.79%和99.05%。     

微波水热法制备稀土元素铒掺杂TiO_2光催化剂及光催化活性

采用微波水热法和溶胶-凝胶法制备稀土元素Er掺杂TiO_2光催化剂TiO_2-Er,以甲基橙溶液为模拟污染物,在微波辐射-紫外光照(MW-UV)和太阳光照条件下,考察TiO_2-Er光催化剂的光催化降解活性。分别用N_2吸附-脱附、ICP-AES和PL光谱分析对TiO_2-Er光催化剂进行结构测试和表征。结果表明,Er掺杂能显著提高TiO_2光催化剂光催化活性,微波水热法制备的TiO_2-Er光催化剂具有较高的光催化活性;微波水热法和溶胶-凝胶法制备的TiO_2-Er光催化剂微波辐射-紫外光照50 min,甲基橙降解率分别为100%和98.5%,太阳光照4 h,甲基橙降解率分别为99.0%和97.5%。微波水热法具有晶化时间短和元素掺杂均匀的优点,制备的TiO_2-Er光催化剂具有形貌均匀、孔径较大、孔分布均匀和比表面积较大等特点,且Er掺杂能抑制光生e~-/h~+复合,使光生e~-/h~+的分离效率得到提高,有利于光催化活性的提高。     

A comparative photocatalytic activity of titanium dioxide and zinc oxide by investigating the degradation of vanillin

The photocatalytic degradation of an organic pollutant such as vanillin has been investigated in aqueous suspensions of titanium dioxide and zinc oxide by monitoring the change in substrate concentration employing UV spectroscopic analysis and decrease in Total Organic Carbon (TOC) content as a function of irradiation time under a variety of conditions. The degradation of the model compound was studied under different conditions such as pH, catalyst concentration, substrate concentration and in the presence of an electron acceptor such as hydrogen peroxide besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts, Hombikat UV100 and ZnO.     

pH dependent morphology and texture evolution of ZnO nanoparticles fabricated by microwave-assisted chemical synthesis and their photocatalytic dye degradation activities

ZnO nanostructures are well-known photocatalysts for the degradation of toxic organic dyes and their morphology, size, and other physicochemical properties play important roles in their photocatalytic performance. To study the effect of size, morphology, and synthesis conditions in photocatalytic performance, we synthesized ZnO nanoparticles of different morphologies through a simple microwave-assisted chemical process at different pH values of the reaction mixture. Different pH values of the reaction mixture produced ZnO nanoparticles of different morphologies and sizes. The nature of the pH controlling agent and final pH of the reaction mixture were seen to have considerable effects on the lattice parameters and microstrain of the ZnO nanocrystals, along with their photocatalytic performance. We observed that while the ZnO nanostructures synthesized at very high pH values of the reaction mixture have a high specific surface area, their photocatalytic activity is higher when they are synthesized at acidic pH or pH near the isoelectric point of ZnO. The results demonstrate that the photocatalytic activity of ZnO nanostructures not only depends on their size or specific surface area but also strongly depends on the concentration of catalytic sites at their surface.     

BiOCl and TiO2 deposited on exfoliated ZnCr-LDH to enhance visible-light photocatalytic decolorization of Rhodamine B

A series of novel TiO₂-BiOCl-ZnCr-Ex composites for use as photocatalysts were synthesized via a facile solvothermal process using an exfoliated ZnCr-LDH (ZnCr-Ex) and depositing BiOCl and TiO₂ sequentially on the surface of ZnCr-Ex. The composites were characterized by XRD, TEM, SEM-EDS and UV–vis diffuse reflectance spectroscopy. In these composites, the BiOCl nanosheets were deposited first on the surfaces of ZnCr-Ex and then the TiO₂ nanoparticles were dispersed on the surface of BiOCl-ZnCr-Ex material as were seen from SEM and TEM analyses. The photocatalytic degradation of Rhodamine B (RhB) indicated that the TiO₂-BiOCl-ZnCr-Ex composite showed much higher visible-light photocatalytic activity for degradation of RhB than TiO₂ alone, BiOCl alone or the BiOCl-ZnCr-Ex by itself. The possible mechanisms of photocatalytic activity were discussed. Moreover, the present composite photocatalysts exhibited satisfactory re-usability for at least three cycles. Because of the facile synthesis process, higher photocatalytic activity under visible light irradiation and satisfactory re-usability of these composites, they can be touted as potential catalysts for degradation of organic pollutants in wastewater treatment.     

Review MXenes as a new type of nanomaterial for environmental applications in the photocatalytic degradation of water pollutants

Two-dimensional titanium carbide (MXene) with an adjustable bandgap (0.92–1.75eV), excellent structural stability, high conductivity and hydrophilicity has always been a hotspot in the field of environmental photocatalysis. However, the rapid recombination of light-excited carriers of a single photocatalytic material decreases quantum efficiency and photocatalytic performance. The modification of MXene could overcome these problems to improve photocatalytic properties. Among various improvement strategies, the composition of MXene heterostructure and Schottky junction is an effective and straightforward strategy for adjusting electronic structure and accelerating photocatalytic performance. This review aims to design typical, cost-effective heterojunctions and Schottky junctions and their progress, mechanisms, and trends in environmental organic pollutants' degradation. This review detailed the heterogeneous catalytic mechanism of MXene-based photocatalysts for the degradation of organic pollutants. It is discussed the way to improve the photocatalytic performance of MXene by constructing heterojunction and Schottky junction. The surface properties, catalyst performance and pollution management of various MXene-based catalysts were compared, and then some dilemmas and application strategies of MXene development were analyzed in depth. This review can open up ideas for new approaches and provide valuable clues for designing MXene as a cocatalyst to develop more effective photocatalysts for practical application in environmental pollution management.     

Ag3PO4/AgI光催化剂的制备及降解2-氨基-4-乙酰氨基苯甲醚机理

研究了Ag₃PO₄复合棒状AgI光催化剂的制备及降解2-氨基-4-乙酰氨基苯甲醚（AMA）的性能和机理,利用X射线衍射（XRD）、扫描电镜（SEM）、紫外可见漫反射（UV-Vis）、光电子能谱（XPS）等方法对合成样品的物相组成和形貌结构进行了表征。通过可见光催化降解AMA来评价光催化剂的催化性能。实验结果显示,Ag₃PO₄/AgI复合光催化剂比Ag₃PO₄和AgI单体具有更强的光催化氧化与还原能力,其中以I和P的比例为1∶5时效果最佳,且在五次循环使用之后仍有较好的光催化活性。自由基捕获实验证明光催化过程中光生空穴（h⁺）是主要的活性物种。投加量为30mg、光照时间60min的条件下可将AMA几乎完全去除。本文研究结果为构筑新型可见光光催化剂提供了新视角,为促进光催化降解有机污染物提供了新途径。     

Effect of modified graphene quantum dots on photocatalytic degradation property

The effective use of solar energy in sewage disposal has been extensively investigated. This work focuses on the photocatalytic property of graphene quantum dots (GQDs) and polymer-modified GQDs under visible light. A hydrothermal synthesis route to GQDs was developed by using citric acid as a carbon precursor. The GQDs were modified with polyethylenimine (PEI) and polyethylene glycol (PEG). The obtained GQDs, GQDs-PEIs, and GQDs-PEGs were characterized and their structural information was determined through Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), photoluminescence spectroscopy, and UV–Vis absorption spectroscopy. Results revealed that the GQDs were uniform in size (2–5 nm) and rich in oxygen-containing groups. The GQDs exhibited a strong blue and excitation-independent photoluminescent behavior under excitation wavelengths of 320–420 nm. The photocatalytic performance of these samples was demonstrated on the basis of methylene blue (MB) degradation. The photocatalytic rates of GQDs, GQDs-PEIs, and GQDs-PEGs decreased successively. The polymer-modified GQDs could qualitatively control the degradation rate of MB. Free radical species were generated to oxidize MB under light irradiation. Thus, photocatalytic organic matter degradation, sustained drug release, and tracking can be combined to implement proper sewage disposal.Prime noveltyThe main object of this work is to find out a novel property of graphene quantum dots (GQDs) as efficient nanomaterials for degradation of organic pollutant dyes under visible light irradiation. And, the GQDs exhibited a strong blue and excitation-independent photoluminescent behavior under excitation wavelengths of 320–420 nm. Moreover, the degradation rate could be qualitatively controlled by using different polymer-modified GQDs. Thus, photocatalytic organic matter degradation, sustained drug release, and tracking can be combined to implement proper sewage disposal. Also, the degradation mechanism is discussed.     

Development of highly efficient cost-effective CdS/Ag nanocomposite for removal of azo dyes under UV and solar light

Water pollution by toxic dyes is an environmental problem that threatens human health. A green technology to solve this problem is the use of highly efficient photocatalysts under visible/solar light to degrade these organic molecules. However, develop affordable photocatalytic particles with high luminescence performance, enhanced stability, and low degradation is still a challenge. Here, it is reported the hydrothermal synthesis of an advanced and cost-effective nanocomposite based on a ceramic, cadmium sulphide, covered by silver nanoparticles (CdS/Ag), with outstanding photocatalytic efficiency for toxic dyes degradation under ultraviolet and direct solar light. The CdS/Ag nanocomposite completely degrade the Reactive Red 120 (RR 120), Acid Black 1 (AB 1) and Direct Blue 15 (DB 15) dyes in both light irradiations. Without scavenger, about 93% of degradation was observed at 75 min, remaining a high stability (more than 90%) after fourth degradation cycles.     

色氨酸辅助合成光催化活性增强的球形纳米TiO2

以L-色氨酸（L-Trp）为生物模板,采用简单水解及煅烧后制备了球形结构TiO₂纳米光催化剂。通过X射线衍射、扫描电子显微镜、红外光谱、紫外-可见漫反射光谱、光致发光光谱和N₂吸附-解吸等方法对制得的TiO₂纳米材料进行表征。在催化剂合成过程中,L-Trp作为生物模板发挥至关重要的作用,能够指导球形结构纳米TiO₂的形成。考察了不同煅烧温度下制备的TiO₂样品光催化活性,结果表明550℃时制备的TiO₂样品具有优异的光催化活性,紫外光照射30min对甲基橙溶液的降解率达到95%左右,主要是由于较大比表面积和球形结构的协同效应。光催化剂稳定性实验表明,所制备的TiO₂纳米材料可作为一种实用有效的光催化剂用于紫外光照射下降解有机染料。同时,对L-Trp辅助下球形结构TiO₂纳米颗粒的可能生长机理进行讨论。     

Enhanced Visible-Light Photocatalytic Degradation of Humic Acid by Palladium-Modified Nitrogen-Doped Titanium Oxide

Palladium-modified nitrogen-doped titanium oxide (TiON/PdO) nanoparticles were synthesized by a sol–gel process, for visible-light-induced photocatalysis using humic acid (HA) as a target. Our work shows that palladium modification has strong effects on the optical and photocatalytic properties of nitrogen-doped titanium oxide (TiON) photocatalysts. TiON/PdO nanoparticles demonstrated an enhanced photocatalytic activity over TiON within a narrow range of palladium concentration. Beyond this range, the adverse effect of palladium modification was observed in the visible-light-induced degradation of HA. The effects of palladium modification are discussed in terms of its role in controlling electron–hole recombination.     

Structure and photocatalytic performance of magnetically separable titania photocatalysts for the degradation of propachlor

A magnetic photocatalyst was prepared by modification of TiO₂ nanoparticles (Degussa P25) with nanocrystalline γ-Fe₂O₃ nanoparticles through a protective lining made up of two oppositely charged polyelectrolytes. As-prepared magnetically separable photocatalysts differing in γ-Fe₂O₃ loading (3, 8, 13, 20 and 30 wt.%) were characterized by XRD, TEM, thermal analysis, Mössbauer and magnetic measurements. The photocatalytic efficiency of the nanocomposite catalysts was evaluated using a chloroacetanilide herbicide (propachlor) in water as model compound. The primary degradation of propachlor followed pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Generally, all magnetic photocatalysts exhibit good catalytic activity towards organic pollutants, do not suffer from photodissolution and can be reused several times without any decrease in their photocatalytic activity.     

Synthesis of magnetically recyclable porous CoFe2O4/Rh composites with large BET surface area for enhanced photocatalytic degradation of organic pollutant

The organic pollutants in water have been a great environment challenges to human beings, and photocatalytic degradation is an effective method to solve this problem. In this paper, the Rh-loaded cobalt ferrite CoFe₂O₄ (CFO) nanoparticles have been successfully synthesized by in situ photodeposition of Rh nanoparticles onto the porous CFO particles as the photocatalysts. After incorporating Rh nanoparticles, the CFO/Rh composite has a higher specific surface area and is more efficient in charge separation than the bare CFO. The photocatalytic efficiency of decomposing Malachite Green (MG) is improved from 70% over the bare CFO to 97% over the optimized CFO/Rh in 60 min. The CFO/Rh sample also demonstrates its durability for the degradation of MG in 5 photocatalytic reaction cycles. Additionally, hydroxyl radicals (?OH) and superoxide radicals (?O₂^?) are proved to be the crucial reactive species during the photocatalytic degradation of MG with CFO/Rh, evidenced by the active species capture experiments. This work provides a useful approach to enhance the photocatalytic activity of semiconductors for degrading organic dyes.     

ZnO/碳纳米管复合光催化材料对抗生素的光催化降解

采用溶胶法合成了ZnO/碳纳米管复合光催化材料,采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、紫外-可见漫反射吸收光谱(UV-Vis)等手段对复合催化剂进行了表征。以氙灯(250～800 nm)为光源,盐酸四环素为降解对象,评价样品的光催化活性。比较ZnO/CNTs复合材料和纯ZnO对抗生素的降解能力,并考察光催化剂的重复利用能力。结果表明,通过溶胶法得到了在碳纳米管表面均匀、致密包覆ZnO颗粒的复合材料。由于ZnO/CNTs材料良好的吸附性能,其光催化活性高于纯ZnO,在300 W氙灯光源下反应2 h,对盐酸四环素的降解率达82.38%,同时复合材料显示了抑制ZnO光蚀的能力。     

基于孔材料的多元复合光催化剂降解抗生素

多孔复合材料光催化体系集多孔材料的吸附性能和光催化活性,可将水体中浓度较低的抗生素富集在光催化活性位表面进行高效降解,同时吸附性能得以原位再生。通过对光催化活性体与载体的结构调控,可获得更宽的吸光范围（包括可见光）且有效抑制光生电子-空穴对复合。本文总结了基于新型多孔材料包括石墨烯、金属有机框架材料（MOFs）、多孔有机聚合物（POPs）等与传统半导体构筑的多元光催化体系及其对水体中抗生素等有机污染物光降解的最新研究进展,阐述了多元光催化体系设计思路、降解过程优化控制因素、抗生素降解去除性能及其产生优异性能的机理。此外,还总结了当前复合光催化剂在结构设计和性能评价层面存在的问题,最后对光催化材料的研究方向进行了展望,借助光响应的多孔有机聚合物提升复合光催化剂性能以及粉末光催化剂材料的工程化应用探究将有效促进光催化技术的发展。