负载型纳米Au催化剂光催化性能的研究进展

金纳米颗粒对紫外和可见光有较好的吸收,能在温和条件下活化反应分子,从而促使反应发生,并提高反应物转化率和产物选择性,成为新型光催化剂的研究热点。本文介绍了纳米金催化剂的光催化反应机理,光子激发的表面等离子体共振所造成的表面电荷偶极引起亲电子或亲核反应,以及以半导体材料为载体的负载型纳米金催化剂光催化机理。总结了纳米金光催化剂在污染物和染料降解、臭氧分解、硝基化合物还原、选择氧化以及制氢等光催化领域的应用和最新研究进展,并展望了该新型光催化剂的研究发展方向。     

微波合成(Au)_核·(Ag)_壳纳米粒子及其共振散射光谱研究

以柠檬酸化学还原法制备的金纳米粒子作晶种,采用微波高压液相合成技术,制备出分散性较好、规则球形的(Au)核·(Ag)壳复合纳米粒子。研究了(Au)核·(Ag)壳复合纳米粒子的紫外可见吸收光谱和共振散射光谱特性,在470nm处有最强共振散射峰,在404nm处产生一个吸收峰。结果表明,(Au)核·(Ag)壳复合纳米粒子的形成是导致470nm共振散射的根本原因。     

可见光光催化机理研究进展

可见光光催化作为多相光催化研究的热点，日益受到重视，采用染料光敏化、离子掺杂、半导体复合和增加晶体缺陷等方式对半导体进行改性实现可见光光催化，并提出相关的可见光光催化机理。结合近年来半导体光催化剂的不同改性方式，从电子、空穴不同的激发途径上，对可见光光催化机理进行评述，为可见光光催化剂的研究提供指导。     

(Ag)_核·(Au)_壳复合纳米粒子的制备

以银原子团簇作晶种,采用微波高压液相合成法制备了分散性好、规则球形的(Ag)核·(Au)壳复合纳米粒子。研究了(Ag)核·(Au)壳复合纳米粒子的紫外可见吸收光谱和共振散射光谱特性。结果表明,液相(Ag)核·(Au)壳复合纳米粒子和高压微波合成的液相金纳米粒子的最强共振散射峰均在580nm处,它们的吸收光谱图相似,最大吸收分别在518.5nm和524.8nm。     

光化学还原制备具有光学活性的NaC修饰的Ag纳米粒子

采用光化学还原法,以胆酸钠为还原剂还原AgNO_3制备出胆酸钠(NaC)修饰的Ag纳米粒子。在紫外光的照射下NaC在反应中作为还原剂,同时还起到稳定生成的银纳米粒子以及作为手性诱导剂的作用。制备的胆酸钠修饰的Ag纳米粒子在442 nm处出现一个CD信号,表现为正的科顿效应峰,对应于Ag纳米粒子的表面等离子体共振(SPR)吸收,该CD信号的出现表明制备的Ag纳米粒子具有光学活性。在可见光区的CD信号随着反应时间的延长而逐渐增强。胆酸钠的浓度会影响生成的Ag纳米粒子的CD信号,随着胆酸钠浓度的减小CD信号逐渐增强。     

碳量子点与半导体复合光催化材料合成及降解有机污染物的应用进展

有机污染物的危害日益严重,引起人们的广泛关注。半导体光催化降解有机污染物是公认的绿色技术,但传统的半导体光催化材料对可见光的利用率低,光生电子与空穴易复合,导致降解有机污染物的效率不高,开发高效、稳定的半导体复合光催化材料,是当前光催化领域的研究热点。碳量子点(CQDs)是新型的纳米级荧光碳材料,可作为修饰剂与半导体材料复合,能够显著提高复合材料的光催化降解效率,极大地激发了研究者的兴趣。本文介绍了碳量子点与半导体光催化剂的复合方法,总结了近几年CQDs/半导体复合光催化材料降解有机染料、抗生素、止痛药、酚类化合物等有机污染物的应用成果。     

钒酸盐掺杂二氧化钛可见光响应的复合光催化剂的研究进展

开发可见光响应和高效稳定的二氧化钛基复合光催化剂是当前的研究热点之一.本文介绍了高活性、高稳定性的窄带隙半导体材料钒酸盐掺杂二氧化钛复合光催化剂的研究进展,重点讨论了钒酸盐掺杂二氧化钛的光催化机理,列举了国内外所取得的成果.     

Au/TiO_2纳米光催化剂的制备及光催化性能研究

采用水热法制备TiO_2纳米粒子,通过光化学还原沉积法制备了Au/TiO_2光催化剂,并利用SEM、XRD、EDS和DRS等技术对样品进行了表征,考察了不同Au含量对TiO_2纳米粒子光催化分解水制氢活性的影响。研究结果表明,通过此方法可以成功地将Au纳米粒子均匀地分散在TiO_2纳米粒子表面,用适量Au进行表面修饰不仅能提高TiO_2对可见光的吸收,还可以促进TiO_2光生电子-空穴对的分离效率,从而提高了TiO_2纳米粒子的光催化活性。其中,3%Au/TiO_2纳米粒子的光催化活性最高。     

Tb掺杂介孔TiO_2/聚噻吩复合材料的制备及其可见光光催化性能研究

采用原位聚合法制备了一系列不同质量比m(Th)/m(Tb掺杂介孔TiO2)的复合光催化剂(其中Th为噻吩),采用XRD、FTIR、荧光光谱(PL)、场发射透射电镜(FETEM)和X射线光电子能谱(XPS)对复合光催化剂进行了表征。结果表明,复合粒子上的聚噻吩骨架中S原子与TiO2粒子间存在相互作用。以罗丹明B为模型降解物,研究了不同比例复合光催化剂在可见光下的光催化性能,其中m(Th)/m(Tb掺杂介孔TiO2)=1/10复合光催化剂光催化性能最好。在可见光照射下4 h,脱色率达到82.4%。这是由于Tb掺杂介孔TiO2与PTh(聚噻吩)之间的协同作用,拓宽了TiO2纳米粒子的光响应范围,提高了光生电子和空穴的分离效率,从而有效提高了其光催化性能。     

纳米TiO2的改性技术及其应用前景

针对半导体纳米TiO2粒子带隙较宽、光利用率低的缺点,对表面光敏化、掺杂过渡金属离子、表面沉积贵金属、复合半导体等几种提高TiO2光催化活性的改性方法进行了综述,介绍了各方法的机理以及研究现状,并对TiO2光催化剂的应用前景进行了展望。     

Hierarchical ZnO/Ag nanocomposites for plasmon-enhanced visible-light photocatalytic performance

Surface plasmon resonance (SPR) of the noble metals improve the photocatalytic activity of semiconductor metal oxides in the visible light region. This work reports the facile preparation of SPR induced visible light active hierarchical ZnO/Ag nanocomposite photocatalysts by using environmental friendly two-step method. The prepared nanocomposites analyzed by using various techniques such as powder-XRD, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV–Vis spectroscopy, photoluminescence spectroscopy, and photocurrent measurements. The results indicate the formation of hierarchical ZnO/Ag nanocomposites, which shows surface plasmon absorbance and enhanced photocurrent responses. Because of the SPR effect, the nanocomposites show improved visible light photocatalytic activity by enhancing the electron-hole pair separation in Rhodamine B degradation system.     

Novel in-situ synthesis of Au/SnO2 quantum dots for enhanced visible-light-driven photocatalytic applications

In recent years, visible-light-driven metal–semiconductor nanocomposites have emerged as a suitable material for the decomposition of various water and air pollutants. In this work, a novel plasmonic Au nanoparticle (NP)/SnO₂ quantum dot (SQD) nanocomposite photocatalysts were prepared via a one-step solvothermal technique. The as-prepared plasmonic photocatalysts were characterized by various techniques, and the results established the formation of Au/SQD nanocomposites. The photocatalytic activity of the as-prepared plasmonic Au/SQD nanocomposites was examined by the degradation of Rhodamine B (RhB) at room temperature under visible light, and the Au/SQD photocatalyst, prepared using 1.0?g of tin chloride, exhibited a higher rate constant of RhB degradation than pristine SQDs. This exceptional improvement in catalytic performance under visible light is ascribed to a shift of the band gap from the ultraviolet to the visible region. The surface plasmon resonance effect of Au NPs and the synergistic coupling of the metal and the semiconductor QDs also played a vital role in enhancing the catalytic performance. The process of the photocatalytic degradation of RhB by the Au/SQD nanocomposites under visible light is described.     

Preparation and visible light photocatalytic activity of Ag/TiO₂/graphene nanocomposite

Great efforts have been made to develop efficient visible light-activated photocatalysts in recent years. In this work, a new nanocomposite consisting of anatase TiO(2), Ag, and graphene was prepared for use as a visible light-activated photocatalyst, which exhibited significantly increased visible light absorption and improved photocatalytic activity, compared with Ag/TiO(2) and TiO(2)/graphene nanocomposites. The increased absorption in visible light region is originated from the strong interaction between TiO(2) nanoparticles and graphene, as well as the surface plasmon resonance effect of Ag nanoparticles that are mainly adsorbed on the surface of TiO(2) nanoparticles. The highly efficient photocatalytic activity is associated with the strong adsorption ability of graphene for aromatic dye molecules, fast photogenerated charge separation due to the formation of Schottky junction between TiO(2) and Ag nanoparticles and the high electron mobility of graphene sheets, as well as the broad absorption in the visible light region. This work suggests that the combination of the excellent electrical properties of graphene and the surface plasmon resonance effect of noble metallic nanoparticles provides a versatile strategy for the synthesis of novel and efficient visible light-activated photocatalysts.     

Ag/AgX（X=Cl,Br,I）等离子共振光催化剂的研究进展

银/卤化银[Ag/AgX（X=Cl,Br,I）]光催化剂作为一种新型光催化剂,由于在可见光区域具有明显的等离子共振效应从而显示了优异的可见光催化降解有机污染物的活性,引起了人们的极大重视。本文主要对Ag/AgX（X=Cl,Br,I）等离子体光催化剂的结构、光催化降解有机物机理、催化剂制备等进行了综述。Ag/AgX（X=Cl,Br,I）的活性普遍较高,通过半导体复合及形貌尺寸的控制,光催化性能得到进一步改善。进而论述了Ag/AgX体系等离子体共振光催化剂在工业染料废水处理上的应用现状,并对Ag/AgX（X=Cl,Br,I）等离子体光催化剂在高浓度、成分复杂污水体系处理中的应用进行了展望。     

One-pot solvothermal synthesis of carbon dots/Ag nanoparticles/TiO2 nanocomposites with enhanced photocatalytic performance

In this paper, we reported a “green” and facile method for one-pot solvothermal synthesis of carbon dots (CDs)/Ag nanoparticles (AgNPs)/titanium dioxide (TiO₂, commercial Degussa P25) ternary nanocomposites with enhanced photocatalytic performance. The characterizations of this ternary photocatalyst were studied at length and our results revealed that the crystalline phase of TiO₂ component remained unchanged after the reaction. While the newborn AgNPs and CDs were tightly attached onto the surface of TiO₂ nanoparticles. The photocatalytic activities of photocatalysts were tested by measurements of photo-degradation on methylene blue (MB) under ultraviolet (UV) and visible light. It was showed that the photocatalytic performance of the ternary photocatalyst was superior to that of single TiO₂ or CDs/TiO₂ binary photocatalyst. It was probably attributed to the synergistic effect of the photoelectrical properties of CDs and the surface plasmon resonance (SPR) effect of AgNPs, which could both enhance the absorption of visible light and hinder the recombination of photogenerated electron-hole pairs.     

Plasmonic enhancement of photocatalytic decomposition of methyl orange under visible light

By integrating strongly plasmonic Au nanoparticles with strongly catalytic TiO₂, we observe enhanced photocatalytic decomposition of methyl orange under visible illumination. Irradiating Au nanoparticles at their plasmon resonance frequency creates intense electric fields, which can be used to increase electron–hole pair generation rate in semiconductors. As a result, the photocatalytic activity of large bandgap semiconductors, like TiO₂, can be extended into the visible region of the electromagnetic spectrum. Here, we report a 9-fold improvement in the photocatalytic decomposition rate of methyl orange driven by a photocatalyst consisting of strongly plasmonic Au nanoparticles deposited on top of strongly catalytic TiO₂. Finite-difference time-domain (FDTD) simulations indicate that the improvement in photocatalytic activity in the visible range can be attributed to the electric field enhancement near the metal nanoparticles. The intense local fields produced by the surface plasmons couple light efficiently to the surface of the TiO₂. This enhancement mechanism is particularly effective because of TiO₂’s short exciton diffusion length, which would otherwise limit its photocatalytic efficiency. Our electromagnetic simulations of this process suggest that enhancement factors many times larger than this are possible if this mechanism can be optimized.     

具有可见光活性的光催化剂研究进展

简述了可见光光催化机理,该机理与紫外光光催化机理的不同之处在于其电荷传输与分离机制。综述了近年来具有可见光活性的光催化材料的研究进展。贵金属、过渡金属及其化合物的掺杂、染料光敏化、氮掺杂和在适当载体上的负载可使复合物的复合禁带宽度小于TiO2的禁带宽度,从而使TiO2的吸收带发生红移,实现可见光响应,其中,氮掺杂ZnO或氮掺杂TiO2及其复合半导体具有较好的可见光光催化活性,另外一些氮氧化物、氮化物及许多钙钛矿型半导体可以作为可见光分解水的有效催化剂。     

Nanoscale zinc oxide based heterojunctions as visible light active photocatalysts for hydrogen energy and environmental remediation

ABSTRACT

In the recent years, zinc oxide has emerged as one of the promising alternate materials to titania for photocatalytic applications due to its several advantages properties. This review recapitulates the ongoing advancement in the field of ZnO-based heterojunctions as visible light responsive photocatalysts for energy conversion (hydrogen evolution) and environmental remediation (pollutants degradation) applications. After a short introduction about zinc oxide materials, the various approaches utilized in the design and development of efficient ZnO-based nanoheterostructures has been discussed in detail. Specifically, strategies such as coupling ZnO with other semiconductors, supporting on carbonaceous materials, decorating with noble metal nanoparticles, doping with heteroatoms and engineering defects in the semiconductor material have been elaborated with a particular emphasis on hydrogen energy and organic pollutants removal. Finally, the future perspective of this material has been highlighted. This comprehensive review not only summarizes the recent literature in this topic, but also provides a detailed insight on the scope of this material for hydrogen energy and environmental remediation applications.     

Enhanced photocatalytic hydrogen evolution over TiO2/g-C3N4 2D heterojunction coupled with plasmon Ag nanoparticles

2D heterojunction based on g-C₃N₄ nanosheets with other semiconductor nanosheets is a promising way to improve photocatalytic hydrogen evolution (PHE) activity over g-C₃N₄. However, current 2D heterojunction based on g-C₃N₄ are unsatisfactory due to their insufficient absorption of visible light and inefficient charge separation. In this work, Ag/TiO₂/g-C₃N₄ nanocomposites based on 2D heterojunction coupling with Ag surface plasmon resonance (SPR) were synthesized by a method combining facile wetness impregnation calcination. The PHE activity of Ag/TiO₂/g-C₃N₄ nanocomposites is attributed to the TiO₂/g-C₃N₄ 2D heterojunction and bare g-C₃N₄ nanosheet under visible light irradiation, indicating a cooperative effect between Ag and TiO₂/g-C₃N₄ 2D heterojunction. As a result of SPR effect, the composites strongly absorb visible light. In addition, the oscillating hot electrons from Ag can easily transfer to 2D heterojunction. This synergistic effect lead to sufficient visible light absorption and efficient charge separation of 2D heterojunction, which improved the PHE activity of g-C₃N₄. This work indicates that loading metal nanoparticles on 2D heterojunction as metal SPR-2D heterojunction nanocomposites may be a potential method for harvesting visible light for PHE.     

提高TiO_2可见光分解水制氢活性的研究进展

近年来通过能带调控等手段实现TiO2光催化剂的可见光化被广泛研究,并取得了令人注目的进展。综述了提高TiO2可见光产氢活性各种手段,包括金属沉积、金属离子掺杂、染料敏化、阴离子掺杂和半导体复合等的研究进展情况,并对未来的研究方向作了展望。