利用地球上丰富的炭黑和NiS_2双助催化剂修饰提高CdS纳米片体系的可见光产氢活性(英文)

光催化产氢技术是目前解决能源和环境问题的最有潜力的方法之一,因此制备安全高效的光催化剂已成为目前的研究热点.在目前研究的各种光催化剂中,CdS光催化剂因为具有较窄的带隙(2.4 eV)和合适的导带位置,所以在可见光催化产氢领域受到广泛关注.然而,光生电子/空穴对易复合和光腐蚀作用极大地限制了CdS光催化剂的放大应用.因此,人们采用众多改性策略以提高CdS光催化剂的可见光产氢活性,其中构建CdS纳米结构和负载助催化剂被认为是最有效的方式.构建CdS纳米结构既可以缩短载流子的迁移路径,也可以减少CdS晶体中的缺陷.很多不同纳米结构的CdS光催化剂已经被开发,例如纳米线、纳米颗粒和纳米棒等.因为制备过程极为复杂繁琐,所以CdS纳米片的研究鲜见报道.本文采用乙酸鎘和硫脲为原材料,通过简单的溶剂热法合成了CdS纳米片.在CdS的各类助催化剂中,由于常用的Pt,Ag和Au等贵金属的高成本和低储量等问题严重限制了它们的实际应用,所以近年来众多非贵金属助催化剂(例如MoS_2,WS2,NiS,NiO和WC等)得到了广泛关注.由于非贵金属助催化剂存在弱电导率和低功函数等问题,影响了对光生电子的收集和利用.纳米碳材料具有极高的电导率、强可见光吸收、有效的载流子分离和较多的反应位点等优点,因此组合纳米碳材料和非贵金属助催化剂被认为是一种有效的解决方案.本文首次采用炭黑和NiS_2作为双助催化剂改性CdS纳米片,通过简单的溶剂热/沉淀两步法成功合成了廉价高效的CdS/CB/NiS_2三元光催化体系.光催化产氢性能测试表明,CdS-0.5%CB-1%NiS_2展现出最高的光催化效率(166.7μmol h~(-1)),分别是CdS NSs和CdS-1.0%NiS_2的5.16和1.87倍.X射线衍射、高分辨电子显微镜和X射线光电子能谱结果证实了CdS催化剂的片状结构,且炭黑和NiS_2成功负载在CdS纳米片表面.紫外-可见漫反射结果表明,随着炭黑和NiS_2的负载,复合催化剂的吸收边缘产生明显的红移,且对可见光的吸收增强.荧光光谱、阻抗和瞬态光电流曲线测试结果证明,炭黑和NiS_2的加入可以有效地促进光生电子/空穴对分离.极化曲线结果表明,加入炭黑和NiS_2可以降低CdS的产氢过电势,因此加速表面产氢动力学.总之,炭黑和NiS_2之间显著的协同效应极大地提高了可见光吸收,促进光生电子/空穴对分离,加速表面产氢动力学,最终得到了三元光催化体系极高的光催化产氢活性.     

Novel heterostructured Bi(2)S(3)/BiOI photocatalyst: facile preparation, characterization and visible light photocatalytic performance

Novel Bi(2)S(3)/BiOI heterostructures were successfully synthesized through a facile and economical ion exchange method between BiOI and thioacetamide (CH(3)CSNH(2)), and characterized by multiform techniques, such as XRD, Raman, FT-IR, XPS, SEM, TEM, HRTEM, SAED, BET and DRS. The obtained Bi(2)S(3)/BiOI photocatalysts showed excellent photocatalytic performance for decomposing organic dye methyl orange (MO) compared with pure BiOI under visible light irradiation (λ > 420 nm). Among the Bi(2)S(3)/BiOI photocatalysts with different molar percentage of Bi(2)S(3) to initial BiOI (from 2 to 8%), 4% Bi(2)S(3)/BiOI exhibited the highest photocatalytic activity with apparent k(app) of 0.2968 h(-1). Differently, Bi(2)S(3)/BiOI displayed low photocatalytic activity for many colorless organic substrates, such as phenol, 2-chlorophenol, dimethyl phthalate and 5-sulfosalicylic acid. Moreover, the study on the mechanism suggested that the enhanced photocatalytic activity mainly resulted from the role of Bi(2)S(3)-BiOI heterojunctions formed in the Bi(2)S(3)/BiOI, which could lead to efficient separation of photoinduced carriers.     

增强可见光催化活性的Z型MoO3/Bi2O4复合光催化剂的制备（英文）

全球工业化进程的加快使人们饱受环境污染问题的困扰.半导体光催化技术作为一种高效、绿色、有潜力的新技术,在环境净化方面有着广阔的应用前景.Bi2O4是近年来新开发出的一种铋基光催化剂,在环境净化方面已有一些研究.但是,单体光催化剂通常存在光响应范围窄、光生载流子复合率高等问题,这些不足限制了Bi2O4的进一步应用.因此,需要通过适当的改性来拓宽其光响应范围和提高其载流子的分离效率,从而提高其光催化活性.构建Z型异质结被认为是提高光催化剂光生载流子分离效率并进一步提高光催化活性的有效方法.MoO3是一种宽禁带的n型半导体,具有独特的能带结构、光学特性和表面效应,是一种非常有前景的半导体光催化剂.虽然MoO3材料的光生载流子复合率高,带隙(2.7-3.2 eV)大,不利于其参与光催化反应,但MoO3与其他合适的半导体配位形成复合材料后能够有效提高其光生载流子的分离效率,从而提高其光催化活性.本研究采用简单的水热法制备了一种新型Z型MoO3/Bi2O4复合光催化剂,SEM和TEM分析结果表明,MoO3和Bi2O4紧密结合在一起.X射线光电子能谱分析表明,MoO3和Bi2O4之间存在很强的界面相互作用,这有助于电荷转移和光生载流子的分离.光致发光光谱、电阻抗和光电流测试也证明了MoO3/Bi2O4复合光催化剂的光生载流子分离效率更高,形成了更强的光电流.通过在可见光下降解RhB溶液评价了所合成光催化剂的光催化性能.15%MoO3/Bi2O4(15-MB)复合光催化剂表现出了最佳的可见光催化活性,在40 min内对10 mg/L RhB溶液的降解率达到了99.6%,其降解速率是Bi2O4的2倍.此外,15-MB复合光催化剂在经过五次循环降解RhB溶液后仍保持良好的光催化活性和稳定性,表明MoO3/Bi2O4复合光催化剂具有较强的应用潜力.通过自由基捕获实验确定了光催化反应中主要的活性自由基为 O2-和h+.通过莫特-肖特基测试和带隙计算得到MoO3和Bi2O4的价带和导带位置.最后,根据实验和分析结果提出了Z型MoO3/Bi2O4复合光催化剂在可见光下降解RhB溶液的机理.本研究为设计铋基Z型异质结光催化剂用于高效去除环境污染物提供了一种有前景的策略.     

异质结构AgCl/Bi2WO6微米球制备、表征及其光催化性能

首先利用水热法制备了由纳米片组装的粒径为1.5–2μm的Bi2WO6微球,然后在微球表面沉积了不同含量的AgCl (5 wt%,10wt%,20wt%,30wt%),制备了异质结构AgCl/Bi2WO6微球光催化剂.利用X射线粉末衍射、扫描电镜、透射电镜、红外光谱、紫外-可见漫反射吸收等手段对所制的光催化剂进行表征,并以紫外光和可见光分别为光源,罗丹明B为降解对象测试了其光催化活性,考察复合不同含量的AgCl对Bi2WO6光催化剂的性能影响.结果表明,沉积AgCl对Bi2WO6的晶体结构、表面性能和光吸收性能没有产生明显影响,但大幅度提高了Bi2WO6的紫外和可见光催化活性.当复合20wt%AgCl时, AgCl/Bi2WO6光催化活性最佳,紫外光下比纯Bi2WO6提高了2.2倍,可见光下提高了1倍.这主要是由于形成的AgCl/Bi2WO6异质结能有效抑制光生电子和空穴的复合,从而提了其光催化性能.     

基于CdS和CdSe纳米半导体材料的可见光催化二氧化碳还原研究进展

Carbon dioxide (CO₂) is one of the main greenhouse gases in the atmosphere. The conversion of CO₂ into solar fuels (CO, HCOOH, CH₄, CH₃OH, etc.) using artificial photosynthetic systems is an ideal way to utilize CO₂ as a resource and reduce CO₂ emissions. A typical artificial photosynthetic system is composed of three key components: a photosensitizer (PS) to harvest visible light, a catalyst (C) to catalyze CO₂ or protons into carbon-based fuels or H₂, respectively, and a sacrificial electron donor (SED) to consume the holes generated in the PS. In most cases, the PS and catalyst are two different components of a system. However, some components that possess both light harvesting and redox catalysis functionalities, e.g., nano-semiconductors, are referred to as photocatalysts. During photocatalysis, the PS is typically excited by photons to generate excited electrons. The excited electrons in the PS are transferred to the catalyst to generate a reduced catalyst. The reduced catalyst is used as an active intermediate to perform CO₂ binding and transformation. The PS can be recovered through a reaction with the SED. Nano-semiconductors have been used as photosensitizers and/or photocatalysts in photocatalytic CO₂ reduction systems owing to their excellent photophysical and photochemical properties and photostability. CdS and CdSe nano-semiconductors, such as quantum dots, nanorods, and nanosheets, have been widely used in the construction of photocatalytic CO₂ reduction systems. Systems based on CdS or CdSe nano-semiconductors can be classified into three categories. The first category is systems based on CdS or CdSe photocatalysts. In these systems, CdS or CdSe nano-semiconductors function as photocatalysts to catalyze CO₂ reduction without a co-catalyst under visible-light irradiation. The CO₂ reduction reaction occurs at the surface of the CdS or CdSe nano-semiconductors. The second category is systems based on CdS or CdSe composite photocatalysts. CdS or CdSe nano-semiconductors are combined with functional materials, such as reduced graphene oxide or TiO₂, to prepare composite photocatalysts. These composite photocatalysts are expected to improve the lifetime of the charge separation state and inhibit the photocorrosion of the nano-semiconductors during photocatalysis. The third category is hybrid systems containing a CdS nano-semiconductor and molecular catalysts, such as nickel and cobalt complexes and iron porphyrin. In these hybrid systems, CdS functions as a photosensitizer and the CO₂ reduction reaction occurs at the molecular catalyst. This review article introduces the construction of artificial photosynthetic systems and the photocatalytic mechanism of nano-semiconductors, and summarizes the representative works in the three aforementioned categories of systems. Finally, the challenges of nano-semiconductors for photocatalytic CO₂ reduction are discussed.     

Enhancement of photocatalytic H2 evolution on CdS by loading MoS2 as Cocatalyst under visible light irradiation

This communication presents our recent results that the activity of photocatalytic H2 production can be significantly enhanced when a small amount of MoS2 is loaded on CdS as cocatalyst. The MoS2/CdS catalysts show high rate of H2 evolution from photocatalytic re-forming of lactic acid under visible light irradiation. The rate of H2 evolution on CdS is increased by up to 36 times when loaded with only 0.2 wt % of MoS2, and the activity of MoS2/CdS is even higher than those of the CdS photocatalysts loaded with different noble metals, such as Pt, Ru, Rh, Pd, and Au. The junction formed between MoS2 and CdS and the excellent H2 activation property of MoS2 are supposed to be responsible for the enhanced photocatalytic activity of MoS2/CdS.     

离子交换法制备高光催化活性Bi2WO6@Bi2S3异质结纳米片

社会经济快速发展的同时, 也带来了日益严峻的环境污染问题. 半导体光催化氧化技术因节能环保而在环境领域有广阔的应用前景. 作为最具有代表性的半导体光催化材料, TiO2因为其禁带宽度(3.2 eV)比较大, 只能被紫外光激发, 因而对太阳能的利用率较低. 作为一种最简单的含铋层状氧化物, Bi2WO6的禁带宽度(2.7 eV)相对较小, 可以部分利用太阳光中的可见光, 因而受到广大研究者的青睐. 但是, Bi2WO6光催化材料的可见光响应范围较窄, 仅能被波长小于450 nm的光激发, 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Bi2WO6光催化材料进行结构修饰与改性,采用拓展其光响应范围和抑制载流子复合, 来提高其光催化活性.本文采用离子交换法原位合成了具有核-壳结构的Bi2S3@Bi2WO6纳米片, 充分利用Bi2S3优良的可见光响应性能和半导体异质结光催化剂的构建, 来提高Bi2WO6的光催化活性. 结果表明, 随着Na2S·9H2O用量从0增加到1.5 g, 所得催化剂的光活性不断提高, X3B的降解速率常数由0.40×10-3min-1增加到6.6×10-3min-1, 催化剂活性提高了16.5倍. 当进一步增加Na2S·9H2O的用量时(1.5-3.0 g), 复合催化剂的光活性下降. 这是由于过多Na2S·9H2O的引入导致在催化剂表面生成了没有光活性的NaBiS2层(Bi2S3+ Na2S = 2NaBiS2), 占据了催化剂的活性位点, 阻碍了染料分子与催化剂的直接接触. Bi2WO6@Bi2S3异质结纳米片光活性的提高, 可归因于Bi2S3的敏化作用极大拓展了复合催化剂的光响应范围; 另一方面, Bi2WO6和Bi2S3两者之间的半导体异质结效应有效促进了光生载流子在空间的有效分离, 抑制了光生电子-空穴的复合, 从而提高了复合催化剂的催化效率. 本研究为其他半导体复合材料的原位生长制备提供了新的思路.     

圆盘状Bi2WO6-BiPO4异质结的水热合成及光催化性能

采用水热法制备Bi2WO6-BiPO4异质结光催化剂．利用模拟太阳光照射下的罗丹明B降解实验评价了Bi2WO6-BiPO4复合物的光催化性能．结果表明,Bi2WO6-BiPO4光催化活性比Bi2WO6和BiPO4高得多．当Bi2WO6与BiPO4的摩尔比为1：1时复合光催化剂对罗丹明B的降解率最高．Bi2WO6-BiPO4催化活性增强主要归结为两者之间形成了有效的异质结结构,其内建电场能够促进光生载流子的分离．同时,Bi2WO6的加入增强了其对可见光的吸收．研究表明O2^· -和h^＋在光催化降解过程中是主要的活性物种.     

g-C_3N_4/CdS纳米棒复合光催化剂的制备及其光催化性能

采用简单的水热法制得CdS纳米棒,采用溶剂热法制得g-C_3N_4/CdS纳米棒复合光催化剂(1),其结构和性能经SEM,XRD和UV-Vis(DRS)表征。探究了1在可见光作用下光催化降解模拟有机污染物甲基橙的性能。结果表明:在可见光作用下,与纯CdS纳米棒光催化剂比较,1的催化活性明显提高,稳定性显著增强。     

Bismuth-doped ordered mesoporous TiO2: visible-light catalyst for simultaneous degradation of phenol and chromium

A controllable and reproducible synthesis of highly ordered two-dimensional hexagonal mesoporous, crystalline bismuth-doped TiO(2) nanocomposites with variable Bi ratios is reported here. Analyses by transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy reveal that the well-ordered mesostructure is doped with Bi, which exists as Bi(3+) and Bi((3+x+)). The Bi-doped mesoporous TiO(2) (ms-TiO(2)) samples exhibit improved photocatalytic activities for simultaneous phenol oxidation and chromium reduction in aqueous suspension under visible and UV light over the pure ms-TiO(2), P-25, and conventional Bi-doped titania. The high catalytic activity is due to both the unique structural characteristics and the Bi doping. This new material extends the spectral response from UV to the visible region, and reduces electron-hole recombination, which renders the 2.0% Bi-doped ms-TiO(2) photocatalyst highly responsive to visible light.     

Fe掺杂与天然沸石载体对TiO2光催化活性的影响

以具有多孔结构的天然斜发沸石为载体, FeCl₃和TiCl₄为前驱物制备铁离子掺杂TiO₂光催化剂. 分别在紫外光和太阳光照射下, 研究了Fe-TiO₂, TiO₂/沸石和Fe-TiO₂/沸石对甲基橙溶液(MO)的光催化分解过程, 并通过XRD, AFM, FTIR和吸收光谱等手段, 探讨了Fe和沸石对TiO2的光催化活性的影响. 结果表明, 适当浓度的Fe不仅可以提高TiO₂的光催化效率, 而且能够拓展TiO₂的吸收波长范围至可见光区. 而沸石的引入不仅提高了光催化剂的效率, 而且也增强了光催化剂的抗失活性能.     

Ti(Ⅳ)掺杂Bi_2O_3电子结构和可见光催化活性的原理

密度泛函理论(DFT)计算对掺杂体系新型环境光催化剂设计开发具有指导意义.基于DFT框架下的第一性原理平面波超软赝势方法(USPP),对α、β、γ、δ-Bi2O3晶体几何结构分别进行了优化计算,从理论上得到了Bi2O3的总体态密度(TDOS)和Bi、O原子的分波态密度(PDOS).在此基础上对Bi2O3超晶胞进行Ti(IV)的掺杂计算,讨论了Ti(IV)掺杂对各种Bi2O3的电子结构和光吸收特性的影响.结果表明Ti(IV)掺杂Bi2O3晶体后,Ti(IV)的3d轨道进入禁带并与O2p、Bi6p轨道作用,使禁带宽度(Eg)变小,Bi2O3的吸收边红移,从而有助于Bi2O3光催化活性的改善.通过水热合成法制备的Ti(IV)掺杂Bi2O3样品的紫外-可见光漫反射光谱验证了计算的结果.在光催化降解有机染料结晶紫的实验中,光催化剂活性的改善进一步得到证实.     

氮铋共掺杂TiO2的合成及其可见光催化性能研究

以纳米管钛酸为钛的前驱体,Bi(NO₃)₃·5H₂O为N源和Bi源,采用水热法制备了N、Bi共掺杂的TiO₂;并以甲基橙为目标降解物考察了所制备样品的可见光催化性能(λ≥420 nm).利用XRD、XPS、UV-Vis DRS、TEM等技术对不同条件下制备的产物进行了表征.结果表明,所得样品主要为锐钛矿型,粒径20 nm左右,掺杂的Bi主要以Bi₂O₃和BiONO₃两种形式存在.N元素除了以NO₃^-的形式存在于BiONO₃中,还有少量N以间隙氮掺杂于TiO₂中形成Ti-O-N键.N、Bi共掺杂的TiO₂在可见光下表现出了优越的光催化性能,其中水热温度为130 ℃,Bi/Ti摩尔比为1%时,催化活性最高.催化活性的提高源于N和Bi的掺杂增加了样品对可见光的利用效率,降低了光生电子空穴的复合速率.     

TiO2薄膜光催化还原Hg2+的研究

采用溶胶法制备出TiO2、SO42-/TiO2、CdS/TiO2薄膜光催化剂,研究了TiO2薄膜光催化还原Hg2+的最佳实验条件以及SO42-/TiO2、CdS/TiO2薄膜与TiO2薄膜、TiO2粉体与薄膜之间的光催化活性差异.结果表明:当pH=5.34时,经30 min紫外光照射,Hg2+的还原率达到最大;Hg2+初始浓度越高,光致还原量越低;光源波长越短,Hg2+的还原率越高;当甲醇添加量达到15%(体积比)时,反应30 min后,Hg2+的还原率即达100%;CdS改性薄膜的光催化活性高于未改性薄膜;CdS/TiO2薄膜的光催化活性略高于粉体.     

One-pot hydrothermal synthesis of willow branch-shaped MoS2/CdS heterojunctions for photocatalytic H2 production under visible light irradiation

Willow branch-shaped MoS₂/CdS heterojunctions are successfully synthesized for the first time by a facile one-pot hydrothermal method. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption measurements, diffuse reflectance spectroscopy, and photoelectrochemical and photoluminescence spectroscopy tests. The photocatalytic hydrogen evolution activities of the samples were evaluated under visible light irradiation. The resulting MoS₂/CdS heterojunctions exhibit a much improved photocatalytic hydrogen evolution activity than that obtained with CdS and MoS₂. In particular, the optimized MC-5 (5 at.% MoS₂/CdS) photocatalyst achieved the highest hydrogen production rate of 250.8 μmol h^-1, which is 28 times higher than that of pristine CdS. The apparent quantum efficiency (AQE) at 420 nm was 3.66%. Further detailed characterizations revealed that the enhanced photocatalytic activity of the MoS₂/CdS heterojunctions could be attributed to the efficient transfer and separation of photogenerated charge carriers resulting from the core-shell structure and the close contact between MoS₂ nanosheets and CdS single-crystal nanorods, as well as to increased visible light absorption. A tentative mechanism for photocatalytic H₂ evolution by MoS₂/CdS heterojunctions was proposed. This work will open up new opportunities for developing more efficient photocatalysts for water splitting.     

原位合成具有高可见光催化活性的C3N4/CdS纳米复合材料

以硫氰酸铵和氯化镉为原料,采用无模板混合高温煅烧法一步合成氮化碳/硫化镉纳米晶(C3N4/CdS)的复合半导体材料。采用X射线衍射、傅立叶变换红外光谱和透射电镜等技术对其结构和形貌进行了表征。以有机污染物罗丹明B (RhB)为模拟污染物对复合催化剂的可见光催化活性进行测试。结果表明, C3N4/CdS复合材料中CdS以六方相纳米晶的形式均匀分散; CdS的复合基本不改变C3N4主体结构及聚合度;与纯C3N4相比,复合材料在可见区的光吸收能力有所增强。合适的能带匹配有利于光生载流子的迁移,抑制了其复合速率。在可见光照射下,复合半导体能够更加快速的降解有机污染物,且保持很好的稳定性。     

Bi_(12)O_(17)Br_2和Bi_4O_5Br_2纳米片的简易制备及光催化氧化NO机理的原位漫反射红外光谱研究(英文)

BiOBr因具有合适的能带结构和独特的层状纳米结构而广泛应用于可见光催化领域,但其低的可见光利用率和高的光生电子-空穴对复合率,限制了其实际应用.最近,非整比BiOBr纳米材料表现出了良好的可见光催化性能.本课题组分别采用简易水热法和常温法制备得Bi_(12)O_(17)Br_2和Bi_4O_5Br_2纳米片,并表现出良好的可见光催化性能.然而,对于Bi_(12)O_(17)Br_2和Bi_4O_5Br_2的可见光催化氧化NO的转化路径及反应机理还不清楚.基于此,本文采用射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)、电子自旋共振(ESR)、电子顺磁共振(EPR)和比表面积-孔结构(BET-BJH)等手段研究了Bi_(12)O_(17)Br_2和Bi_4O_5Br_2的理化性能,通过原位红外光谱(in situ DRIFTS)研究了Bi_(12)O_(17)Br_2和Bi_4O_5Br_2的可见光催化氧化NO的转化路径及反应机理.XRD结果表明,在常温碱性环境下,OH~-离子逐步取代BiOBr中的Br-离子制备得单斜晶相Bi_4O_5Br_2;在水热碱性环境下,OH-离子进一步取代Bi_4O_5Br_2中的Br-离子制备得四方晶相Bi_(12)O_(17)Br_2.SEM和TEM结果表明,Bi_(12)O_(17)Br_2是由不规则纳米片堆叠形成的紧密且厚实的层状结构,Bi_4O_5Br_2是由纳米片和纳米颗粒无序堆积形成的多孔疏松结构.BET-BJH测试结果显示,Bi_4O_5Br_2的比表面积和孔容(37.2 m~2/g,0.215 cm~3/g)显著高于Bi_(12)O_(17)Br_2(8.7 m~2/g,0.04 cm~3/g).UV-Vis DRS测试结果显示,Bi_(12)O_(17)Br_2和Bi_4O_5Br_2均显示了良好的可见光吸收能力.可见光催化去除NO的测试结果表明,Bi_4O_5Br_2(41.8%)的光催化活性明显高于Bi_(12)O_(17)Br_2(28.3%).并且,在5次可见光催化循环实验后,Bi_4O_5Br_2(41.1%)表现出良好可见光催化稳定性.ESR测试结果表明,Bi_(12)O_(17)Br_2和Bi_4O_5Br_2参与反应的主要活性物种均为·OH自由基,Bi_4O_5Br_2产生·OH自由基明显强于Bi_(12)O_(17)Br_2.EPR测试结果表明,Bi_4O_5Br_2的氧空位明显多于Bi_(12)O_(17)Br_2,丰富的氧空位更有利于NO的有效吸附.由此可见,Bi_(12)O_(17)Br_2和Bi_4O_5Br_2表现出不同的理化特性.可见光催化氧化NO的原位红外光谱表明,只在Bi_(12)O_(17)Br_2光催化氧化NO的转化路径中会生成中间产物N2O3,表明Bi_(12)O_(17)Br_2和Bi_4O_5Br_2具有不同的NO光催化转化路径.结合上述表征结果认为,Bi_4O_5Br_2比Bi_(12)O_(17)Br_2表现出更优异可见光催化性能的主要原因有以下四个方面为:(1)Bi_4O_5Br_2拥有更高的比表面积和更大的孔容,有利于NO的吸附、反应中间产物的转移和提供更多的活性位点参与光催化反应;(2)Bi_4O_5Br_2可以生成更多的·OH自由基和拥有更强的价带空穴氧化能力;(3)NO中的O原子可以与Bi_4O_5Br_2的氧空位结合,从而提供更多的反应位点;(4)Bi_4O_5Br_2的光催化反应中可以生成中间产物N_2O_3,可以降低NO转化成NO_3~-的反应活化能.     

2D-2D CdS/Cu7S4层状异质结高效可见光光催化产氢（英文）

利用太阳能将水转化为清洁可持续的化学燃料是一种很有前途的策略.光催化水分解制氢技术是有效解决能源可持续发展和环境保护问题的重要技术.CdS由于具有较窄的带隙(2.4 eV)和合适的能带位置而被认为是最有潜力的光催化水产氢催化剂之一.然而,CdS强光的腐蚀性和快速的电子空穴复合导致光催化剂活性低、稳定性差,严重阻碍了CdS光催化剂的广泛应用.为了有效提高光催化产氢活性及稳定性,人们对CdS光催化剂进行了大量改性研究.其中,合理巧妙地加载助催化剂和构造纳米结构CdS被认为是两种极为重要的改性策略,两种策略的有效耦合可以更有效地利用太阳能,实现清洁氢燃料的生成.一方面,各种形貌的CdS光催化剂均已被开发,例如纳米线、纳米棒、纳米片和量子点等.然而,由于制备工艺复杂,在以往的报道中很少有超薄2D CdS纳米片用于光催化产氢.另一方面,由于贵金属(Ag,Pt,Au)的稀缺性和高成本阻碍了其修饰光催化剂的实际应用,所以利用非贵金属助催化剂(MoSx,CuS,Ni3C,WS2,NiS,MXene,CoxP和MoP)修饰CdS提高光催化产氢活性近年来备受关注.对于地球丰富的2D层状助催化剂Cu7S4而言,具有优异的光电催化产氢活性和简单制备方法,但是在光催化产氢领域的应用上未引起足够重视.因此,本文充分利用超薄CdS纳米片以及Cu7S4纳米片各自的独特优势,构建了独特的2D-2D层状异质结,实现了高效协同光催化产氢.我们首先以乙酸镉和硫脲为原料通过一步水热法合成了超薄2D CdS纳米片,并用静电自组装方法制备了CdS/Cu7S4.在可见光下进行了产氢测试,实验结果证实了优化的2D CdS/2%Cu7S4层状异质结在含有Na2S·9H2O和Na2SO3的水溶液中光催化析氢活性最高(27.8 mmol g^-1 h^-1),是原始CdS纳米片(2.6 mmol g^-1 h^-1)的10.69倍.经过4次连续循环反应,CdS/Cu7S4二元复合体系展现出良好的稳定性.为深入探讨高效产氢机制,对纳米级CdS复合材料的光催化物化性能及载流子分离机制进行了表征.通过X射线衍射确定了CdS和CdS/Cu7S4的晶体结构.用高分辨电子显微镜和X射线光电子能谱证实合成了CdS催化剂和Cu7S4助催化剂的超薄纳米片结构且成功复合.用紫外-可见漫反射光谱法对制备的纯CdS和CdS/Cu7S4复合样品的光吸收特性进行了表征.结果表明,在CdS上负载Cu7S4以后,可以明显观察到样品对可见光的吸收能力明显增强.对CdS/Cu7S4进行XPS测试分析,进一步证明了样品中S、Cd和Cu的化学成分和状态.利用PL发射光谱研究了CdS/Cu7S4光催化剂的电荷载流子复合和转移行为.进一步对纯CdS和CdS/Cu7S4复合光催化剂的瞬态光电流响应(I-t曲线)进行了研究,确定了光生载体的分离效率.阻抗是深入研究电荷载流子迁移和界面转移的最有力技术,利用阻抗技术证实CdS/Cu7S4界面高效的载流子分离性能.极化曲线结果表明,加入Cu7S4可以降低CdS的产氢过电势,因此加速表面产氢动力学.由此可见,本文所构建的2D-2D CdS/Cu7S4二元层状异质结可以同时实现光生电子空穴对的快速分离、电子的转移和增加光生电子在表面利用效率,从而最大幅度地提高其光催化水分解产氢活性.本文所采用基于CdS纳米片的2D-2D界面耦合策略可以作为一种通用策略扩展到各种传统半导体纳米片的改性,从而极大地推进高效光催化产氢材料的持续进步.     

Covalent organic framework stabilized CdS nanoparticles as efficient visible-light-driven photocatalysts for selective oxidation of aromatic alcohols

Noble-metal-free photocatalysts with high and stable performance provide an environmentally-friendly and cost-efficient route for green organic synthesis.In this work,CdS nanoparticles with small particle size and different amount were successfully deposited on the surface of covalent organic frameworks(COFs).The deposition of suitable content of CdS on COFs could not only modify the light adsorption ability and the intrinsic electronic properties,but also enhance the photocatalytic activity and cycling performance of CdS for the selective oxidation of aromatic alcohols under visible light.Especially,COF/CdS-3 exhibited the highest yield(97.1%) of benzalde hyde which is approximately 2.5 and 15.9 times as that of parental CdS and COF,respectively.The results show that the combination of CdS and COF can improve the utilization of visible light and the separation of photo-generated charge carriers,and COF with the π-conjugated system as supports for CdS nanoparticles could provide efficient electron transport channels and improve the photocatalytic performance.Therefore,this kind of COF-supported photocatalysts with accelerated photo-induced electrons and charge-carrier separation between semiconductors possesses great potentials in future green organic synthesis.     

铋掺杂二氧化钛纳米颗粒的制备及其可见光催化性能

采用水热法,以纳米管钛酸为前驱物制备了Bi掺杂的TiO₂,并利用X射线衍射、透射电子显微镜、X射线光电子能谱、紫外-可见漫反射光谱等手段对样品进行了表征. 以甲基橙的光催化降解为模型反应评价了样品的可见光催化性能. 结果表明,Bi离子并没有进入TiO₂的晶格中,而是以BiOCl的形式存在. 所制得的BiOCl/TiO₂复合物对甲基橙降解表现出较优越的可见光催化活性;当Bi/Ti摩尔比为1%,水热温度为130℃时,所制催化剂的光催化性能最佳,并对光催化活性提高的机理进行了讨论. 同时,该催化剂对4-氯苯酚降解也表现出较高的光催化性能.