新型间接Z字结型g-C3N4/Bi2MoO6/Bi空心微球等离子共振增强光吸收和光催化性能（英文）

半导体光催化技术是目前最有前景的绿色化学技术,可通过利用太阳光降解污染物或制氢.作为有潜力的半导体催化剂,钼酸铋具有合适的带隙(2.58 eV).但是,由于低的量子产量,钼酸铋的光催化性能并不理想.为了提高钼酸铋的光催化性能,研究者多考虑采取构造异质结的方式.石墨相氮化碳(g-C3N4)能带位置合适,与多种光催化半导体能带匹配,是构造异质结的常用选择.因此,本文选用g-C3N4与钼酸铋复合,构造异质结结构.为了进一步提高光催化性能,多采用负载贵金属(Pt,Au和Pd)作为助催化剂,利用贵金属特有的等离子共振效应,增加光吸收,促进载流子分离,但贵金属价格昂贵.Bi金属单质价格便宜,具备等效的等离子共振效应,是理想的贵金属替代物.钼酸铋可以采取原位还原的方式还原出Bi单质,构造更紧密的界面结构,更有利于载流子传输.Bi的等离子共振效应可以有效提高材料的光吸收能力和光生载流子分离率.本文采用溶剂热和原位还原方法成功合成了一种新型三元异质结结构g-C3N4/Bi2MoO6/Bi(CN/BMO/Bi)空心微球.结果显示,三元异质结结构的最佳配比为0.4CN/BMO/9Bi,该样品表现出最好的光催化降解罗丹明B效率,是纯钼酸铋的9倍.通过计算DRS和XPS的价带数据,0.4CN/BMO/9Bi是一种Z字型异质结.牺牲试剂实验也提供了Z字型异质结的有力证据,测试显示超氧自由基·O^2-(在-0.33 eV)是光催化降解的主要基团.但是,钼酸铋的导带位置低于-0.33 eV,g-C3N4的导带高于-0.33 eV,因此g-C3N4的导带是唯一的反应位点,从而证明了光生载流子的转移是通过Z字型异质结结构实现的.TEM图显示金属Bi分散在钼酸铋表面.DRS和PL图分析表明金属Bi增加了材料的光吸收能力,同时扮演了中间介质的角色,促进钼酸铋导带的电子和g-C3N4价带的空穴快速复合.因此,g-C3N4/Bi2MoO6/Bi的优异光催化性能主要归功于Z字型异质结和Bi金属的等离子共振吸收效应,提高了材料的光吸收能力和光生载流子分离率.     

Pr掺杂Bi_2MoO_6/TiO_2复合纳米纤维的制备及可见光催化性能

以电纺TiO_2纳米纤维为基质,采用溶剂热法制备了稀土Pr掺杂Bi_2MoO_6/TiO_2复合纳米纤维,利用X射线衍射仪、扫描电子显微镜、透射电子显微镜、紫外-可见-近红外分光光度计和荧光光谱仪等对不同样品的物相、形貌和光学性能等进行表征,以甲基橙为模拟有机污染物,考察了样品的光催化性能.结果表明,在复合样品中,Pr~(3+)进入Bi_2MoO_6晶格,部分取代Bi~(3+)形成施主能级,导致能级带隙变窄,不仅有利于提高样品的可见光催化活性,抑制光生电子-空穴对复合,而且还提高了Bi_2MoO_6/TiO_2的光催化活性和稳定性.当Pr的掺杂量为3%(摩尔分数)时,光催化降解甲基橙的效果最佳,可见光照射180 min时降解率达到93.8%,比纯Bi_2MoO_6/TiO_2的降解率有明显提高.     

网状钼酸铋的可见光催化活性

采用无助剂、无模板的水热法成功合成网状Bi2MoO6. pH值对这一形貌的形成起重要作用. 所制备的网状Bi2MoO6样品表现出优异的可见光催化活性,其光催化活性比固相法合成的块状Bi2MoO6样品高得多.     

Enhanced Visible-light Photocatalytic Activity of g-C3N4/Nitrogen-doped Graphene Quantum Dots/TiO2 Ternary Heterojunctions for Ciprofloxacin Degradation with Narrow Band Gap and High Charge Carrier Mobility

Limited visible-light absorption and high recombination rate of photogenerated charges are two main drawbacks in g-C₃N₄-based photocatalysts. To solve these problems, g-C₃N₄/nitrogen-doped graphene quantum dots (NGQDs)/TiO₂ ternary heterojunctions were facilely prepared via a one-step calcining method. The morphology, structure, optical and electrochemical properties of g-C₃N₄/NGQDs/TiO₂ were characterized and explored. The optimal g-C₃N₄/NGQDs/TiO₂ composite exhibits enhanced photocatalytic degradation performance of ciprofloxacin (CIP) compared with the as-prepared g-C₃N₄, TiO₂(P25) and g-C₃N₄/TiO₂ heterojunction under visible light irradiation. The apparent rate constant of the composite is around 6.43, 4.03 and 2.30 times higher than those of g-C₃N₄, TiO₂ and g-C₃N₄/TiO₂, respectively. The enhanced photocatalytic efficiency should be mainly attributed to the improvement of light absorption and charge separation and transfer efficiency, originating from the narrow band gap and high charge carrier mobility. The active species trapping experiments results showed that the h⁺ and ^·O₂^- were the main active species in the degradation process. A possible photocatalytic reaction mechanism of the g-C₃N₄/NGQDs/TiO₂ composite for the enhanced degradation of CIP under visible light irradiation was also proposed.     

具有高效界面电荷转移的0D/2D Bi4V2O11/g-C3N4梯形异质结的设计合成及抗生素降解性能研究

随着工业技术的飞速发展,大量有机污染物被应用于生活的各个领域,由此带来了严重的环境问题。众所周知,半导体光催化技术是一种有效且环境友好的降解去除典型污染物的方法,而光催化剂在该技术的应用中起着关键作用。因此,在光催化污染物降解领域,人们已经尝试研究了各种半导体材料。其中石墨相氮化碳(g-C₃N₄)是近年来公认的“明星”材料之一。因其独特的二维层状结构和良好的可见光响应而引起了人们的极大兴趣。由于带隙较窄(~2.7 eV)、能带结构可调以及良好的物理化学稳定性,g-C₃N₄对太阳光谱的吸收可达450 nm,具有一定的可见光光催化性能。然而,g-C₃N₄在去除抗生素和染料方面的降解效率仍然存在不足,例如光生电荷的快速复合以及空穴的氧化能力弱等。为了优化这种有前景的光催化材料,人们尝试了多种方法来改善g-C₃N₄的电子能带结构,例如金属/非金属元素掺杂、形貌调控和官能团修饰等。最近,人们提出了由两种N型半导体光催化剂组成的梯形异质结理念,它可以利用半导体材料更正的价带和更负的导带。相关结果表明,构筑梯形异质结是提高g-C₃N₄光催化活性的最有效方法之一。因此,本文通过简单的原位溶剂热生长法制备了新型0D/2D Bi₄V₂O₁₁/g-C₃N₄梯形异质结光催化剂。Bi₄V₂O₁₁/g-C₃N₄复合材料对去除土霉素(OTC)和活性红染料展示出了优异的光催化活性。尤其是BVCN-50复合材料对OTC和活性红的降解效率高达74.1%和84.2%,该过程的主要活性物种为·O₂^-。大幅增强的光催化性能归因于Bi₄V₂O₁₁和g-C₃N₄之间形成的梯形异质结保持了光催化体系的强氧化还原能力(Bi₄V₂O₁₁的强氧化能力和g-C₃N₄的强还原能力),并促进了光生电荷的空间分离。此外,金属Bi⁰的表面等离子共振效应可以拓宽异质结系统的光吸收范围。此外,基于高效液相色谱-质谱联用(LC-MS)分析,我们研究了OTC降解过程中可能的中间体和降解路径。这项工作为设计和制备g-C₃N₄基梯形异质结用于抗生素和活性染料降解提供了一种新的策略。     

ZnCuAl-LDH/Bi2MoO6纳米复合材料的构建及其可见光催化降解性能

In this study, pure Bi₂MoO₆ was synthesized via a solvothermal method. A ZnCuAl-layered double hydroxide (LDH)/Bi₂MoO₆ (denoted as LDH/Bi₂MoO₆) nanocomposite was synthesized via a steady-state co-precipitation route using Bi₂MoO₆ as the matric material. LDH was deposited on the surface of Bi₂MoO₆ with a close contact interface. The specific surface area of the resulting LDH/Bi₂MoO₆ composite increased up to 19.1 m²∙g⁻¹ owing to the stacking arrangement between LDH and the Bi₂MoO₆ nanosheets, resulting in the generation of a large number of reactive sites. In addition, the light absorption region of the LDH/Bi₂MoO₆ composite was larger than those of pure LDH and Bi₂MoO₆ because of the formation of a heterojunction structure and the possible quantum size effect. The photocatalytic performance of the as-prepared samples was evaluated by carrying out the degradation of rhodamine B (RhB) using them under visible light irradiation. Compared to pure LDH and Bi₂MoO₆, the LDH/Bi₂MoO₆ nanocomposite exhibited enhanced photocatalytic activity for the degradation of RhB. With an increase in the LDH content, the photocatalytic activity of the LDH/Bi₂MoO₆ composite first increased and then decreased. Although the addition of an optimum amount of LDH was beneficial for the generation of electron-hole pairs, excessive LDH on the surface of Bi₂MoO₆ decreased the visible light absorption ability of both the components, thus reducing photocatalytic activity of the composite. This indicates that an appropriate LDH:Bi₂MoO₆ molar ratio is necessary for obtaining LDH/Bi₂MoO₆ composites with excellent photocatalytic activity. Furthermore, the LDH/Bi₂MoO₆ composite showed high photocatalytic stability and reusability. The structure of the LDH/Bi₂MoO₆ composite remained almost unchanged even after four photodegradation cycles. The enhanced photocatalytic performance of the composite can be attributed to the combined effect of its heterojunction structure and high specific surface area, which are beneficial for effective separation of photogenerated charge carriers and the availability of a large number of active sites for photocatalysis. It was found that •OH and O₂^•− were the main reactive species, while e⁻ and h⁺ contributed little to the photodegradation process. The generation, transfer, and separation of photoinduced electrons and holes in the composites were investigated by transient photocurrent responses, electrochemical impedance spectroscopy Nyquist plots, and photoluminescence measurements. The results showed that the heterojunction structure of the composites played a key role in enhancing their photocatalytic activity. A possible photodegradation mechanism was proposed for the composite. This study will provide a facile approach for the preparation of LDH- and/or Bi₂MoO₆-based nanocomposites. The LDH/Bi₂MoO₆ nanocomposite prepared in this study showed huge potential to be used as a visible-light photocatalyst for degrading environmental pollutants.     

Z型光催化剂Sb2WO6/g-C3N4的制备及光催化性能

通过水热反应合成了Sb₂WO₆改性的g-C₃N₄复合材料(Sb₂WO₆ /g-C₃N₄). 通过X射线衍射(XRD)、 扫描电子显微镜(SEM)、 紫外-可见漫散射反射光谱(UV-Vis DRS)和光致发光光谱(PL)等表征了样品的性质. 结果表明, Sb₂WO₆在g-C₃N₄的表面上生长, 并且复合材料光吸收能力有一定的增强, 光生电子-空穴的重组率降低. 通过罗丹明B(RhB)的光降解评价了Sb₂WO₆/g-C₃N₄复合材料的光催化性能. 结果表明, 模拟日光下Sb₂WO₆质量分数为10%的Sb₂WO₆/g-C₃N₄复合材料在60 min内对RhB的降解率为99.3%, 高于纯g-C₃N₄和Sb₂WO₆. Sb₂WO₆/g-C₃N₄复合材料的这种高度增强的光催化活性主要归因于强的界面相互作用促进了光生电子-空穴分离和迁移. 添加自由基清除剂的实验结果表明, ·O^2-和h⁺是光催化反应中的主要活性物质. Sb₂WO₆/g-C₃N₄复合材料在几个反应周期内表现出优异的稳定性. 根据实验结果提出了一种可能的Z型光催化机理.     

Bi_2MoO_6/BiVO_4异质结的水热合成和可见光催化活性(英文)

采用一步水热法制备Bi2MoO6/BiVO4复合光催化剂.利用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、高分辨透射电子显微镜(HRTEM)等手段对其晶体结构和微观结构进行了表征.结果表明,Bi2MoO6纳米粒子沉积在BiVO4纳米片表面从而形成异质结结构.紫外-可见漫反射光谱(UV-Vis DRS)表明所制备的Bi2MoO6/BiVO4异质结较纯相Bi2MoO6和BiVO4对可见光吸收更强.由于形成异质结结构及其光吸收性能使Bi2MoO6/BiVO4光催化活性有较大提高.可见光下(λ420 nm)光催化降解罗丹明B(RhB)实验结果表明,Bi2MoO6/BiVO4光催化活性较纯相Bi2MoO6和BiVO4高.Bi2MoO6/BiVO4样品光催化性能提高的原因是Bi2MoO6和BiVO4形成异质结,从而有效抑制光生电子-空穴对的复合,增大了可见光吸收范围及比表面积.     

In-situ Construction of Sulfur-doped g-C3N4/defective g-C3N4 Iso-type Step-scheme Heterojunction for Boosting Photocatalytic H2 Evolution

The rational construction of a high-efficiency stepscheme heterojunctions is an effective strategy to accelerate the photocatalytic H₂.Unfortunately,the variant energy-level matching between two different semiconductor confers limited the photocatalytic performance.Herein,a newfangled graphitic-carbon nitride(g-C₃N₄)based isotype step-scheme heterojunction,which consists of sulfur-doped and defective active sites in one microstructural unit,is successfully developed by in-situ polymerizing N,N-dimethylformamide(DMF)and urea,accompanied by sulfur(S)powder.Therein,the polymerization between the amino groups of DMF and the amide group of urea endows the formation of rich defects.The propulsive integration of S-dopants contributes to the excellent fluffiness and dispersibility of lamellar g-C₃N₄.Moreover,the developed heterojunction exhibits a significantly enlarged surface area,thus leading to the more exposed catalytically active sites.Most importantly,the simultaneous introduction of S-doping and defects in the units of g-C₃N₄ also results in a significant improvement in the separation,transfer and recombination efficiency of photo-excited electron-hole pairs.Therefore,the resulting isotype step-scheme heterojunction possesses a superior photocatalytic H₂ evolution activity in comparison with pristine g-C₃N₄.The newly afforded metal-free isotype step-scheme heterojunction in this work will supply a new insight into coupling strategies of heteroatoms doping and defect engineering for various photocatalytic systems.     

碳自掺杂g-C3N4光催化性能的原位光微量热-荧光光谱研究

通过在尿素前驱体中添加单宁酸, 原位缩聚形成碳自掺杂石墨相氮化碳(g-C₃N₄). 利用X射线光电子能谱(XPS)、 场发射扫描电子显微镜(FESEM)、 X射线衍射(XRD)仪和同步热分析(TG-DSC)等方法对碳自掺杂 g-C₃N₄的形貌、 物相结构和能带价态组分进行表征分析, 结合紫外-可见吸收光谱(UV-Vis)和原位光微量热-荧光光谱联用仪获得碳自掺杂g-C₃N₄降解罗丹明B的原位热/动力学信息和三维荧光光谱信息, 探讨了光催化降解罗丹明B的微观机制. 结果表明, 单宁酸浓度≤10 mg/mL时, 碳会取代七嗪单元结构的氮原子形成g-C₃N₄骨架碳自掺杂; 单宁酸浓度≥ 20 mg/mL时, 碳以无定形形式沉积负载在g-C₃N₄表面上形成无定形碳自掺杂. 骨架碳自掺杂g-C₃N₄形成的π电子有效缩短了禁带宽度, 减小了光生电子-空穴复合几率, 比无定形C掺杂g-C₃N₄显示出更优异的光催化性能, 催化主要活性物种为h⁺和·O{}_{\mathrm{2}}^{-}. 碳自掺杂g-C₃N₄光催化降解过程可分为光响应吸热、 降解污染物放热平衡过程和稳定放热3个过程. 其中骨架碳自掺杂g-C₃N₄(C/N摩尔比为0.844)在光照1000 s内, 三维荧光光谱检测的RhB降解率锐减, 光照1000 s后, 其RhB降解率为87.6%, 分别是原始g-C₃N₄和无定形碳自掺杂g-C₃N₄的3.13倍和1.95倍. 光照1000 s后, 光微量热计显示以矿化和降解非荧光发色中间产物为主, 并保持以热变速率为(0.9799±0.5356) μJ/s稳定放热, 为拟零级反应过程, 是光催化反应的决速步骤.     

Heterostructured Nitrogen and Sulfur co-Doped Black TiO2/g-C3N4 Photocatalyst with Enhanced Photocatalytic Activity

Conventional titanium dioxide(TiO₂) photocatalyst could absorb only ultraviolet light due to its wide bandgap. In this paper, black TiO₂ with narrow bandgap was prepared by introducing oxygen vacancies. Meanwhile, nitrogen(N) and sulfur(S) elements were doped to further broaden the visible light response range of TiO₂(NS-BT), and then heterostructured N,S-doped black TiO₂/g-C₃N₄(CN/NS-BT) was successfully constructed by easily accessible route. The formation of CN/NS-BT heterojunction structure increased the generation and separation efficiency of photogenerated electron-hole pairs, as well as accelerated the transfer rate of the carriers. The as-prepared CN/NS-BT exhibited excellent photocatalytic performance towards the degradation of Rhodamine B(RhB) under visible light irradiation with satisfactory stability. The apparent reaction rate constant of CN/NS-BT(0.0079) was 15.8-fold higher than that of commercial P25(0.0005). The structure, morphology, chemical composition and optical properties of the as-prepared CN/NS-BT were characterized by various analytical methods, and possible photocatalytic enhancement mechanism was proposed. Overall, CN/NS-BT composites look promising as photocatalytic material for future environmental treatment.     

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.     

Ni,Co基硒化物修饰g-C3N4光催化产氢研究

Developing novel and efficient catalysts is a significant way to break the bottleneck of low separation and transfer efficiency of charge carriers in pristine photocatalysts. Here, two fresh photocatalysts, g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ hybrids, are first synthesized by anchoring Ni₃Se₄ and CoSe₂ nanoparticles on the surface of well-dispersed g-C₃N₄ nanosheets. The resulting materials show excellent performance for photocatalytic in situ hydrogen generation. Pristine g-C₃N₄ has poor photocatalytic hydrogen evolution activity (about 1.9 μmol·h^-1) because of the rapid recombination of electron-hole pairs. However, the hydrogen generation activity is well improved after growing Ni₃Se₄ and CoSe₂ on the surface of g-C₃N₄, owing to the unique effect of these selenides in accelerating the separation and migration of charge carriers. The hydrogen production activities of G-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ are about 16.4 μmol·h^-1 and 25.6 μmol·h^-1, which are 8-fold and 13-fold that of pristine g-C₃N₄, respectively. In detail, coupling Ni₃Se₄ and CoSe₂ with g-C₃N₄ greatly improves the light absorbance density and extends the light response region. The photoluminescence intensity of the photoexcited Eosin Y dye in the presence of g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ is weaker than that in the presence of pure g-C₃N₄. On the other hand, the upper limit of the electron-transfer rate constants in the presence of g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ is greater than that in the presence of pure g-C₃N₄. Among the g-C₃N₄@Ni₃Se₄@FTO, g-C₃N₄@CoSe₂@FTO, and g-C₃N₄@FTO electrodes, the g-C₃N₄@FTO electrode has the lowest photocurrent density and the highest electrochemical impedance, implying that the introduction of CoSe₂ and Ni₃Se₄ onto the surface of g-C₃N₄ enhances the separation and transfer efficiency of photogenerated charge carriers. In other words, the formation of two star metals selenide based on g-C₃N₄ can efficiently inhibit the recombination of photogenerated charge carriers and accelerate photocatalytic water splitting to generate H₂. Meanwhile, the right shift of the absorption band edge effectively reduces the transition threshold of the photoexcited electrons from the valence band to the conduction band. In addition, the more negative zeta potential for the g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ catalysts as compared with that for pure g-C₃N₄ leads to a notable enhancement in the adsorption of protons by the sample surface. Moreover, the results of density functional theory calculations indicate that the hydrogen adsorption energy of the N sites in g-C₃N₄ is -0.22 eV; further, the hydrogen atoms are preferentially adsorbed at the bridge site of two selenium atoms to form a Se―H―Se bond, and the adsorption energy is 1.53 eV. In-depth characterization has been carried out by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, transient photocurrent measurements, and Fourier transform infrared spectroscopy; the results of these experiments are in good agreement with one another.     

ZnIn2S4/g-C3N4复合材料的制备及可见光催化制氢性能

采用水热方法制备了ZnIn₂S₄/g-C₃N₄复合材料, 并通过X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)、 紫外-可见漫反射光谱(UV-Vis DRS)、 透射电子显微镜(TEM)和荧光光谱(PL)等手段对其结构和性能进行表征. 结果表明, 当ZnIn₂S₄的负载量为20%(质量分数)时, 复合材料表现出最佳的光催化制氢性能, 制氢速率可达到637.08 μmol·g^-1·h^-1, 分别为纯ZnIn₂S₄和纯g-C₃N₄的4倍和37倍. 其原因在于ZnIn₂S₄和g-C₃N₄之间具有紧密的异质结结构, 两者有效的结合改善了组分的能带匹配和界面电荷转移, 从而大幅增强了载流子的分离和迁移, 进而提高光催化的性能.     

S型Sb2WO6/g-C3N4复合光催化剂及其增强的可见光诱导的光催化氧化NO性能

近年来,随着工业化和城镇化的飞速发展,作为一种典型的空气污染物,NOx已经造成严重的环境问题,甚至威胁到人类的身体健康.为了解决这个问题,科研工作者研发了许多NOx去除技术,其中光催化技术被认为是一种能有效地去除空气中NOx的技术.作为一种廉价、无毒、热稳定性强、能带结构合适的光催化材料,石墨相氮化碳(g-C3N4)能够有效的利用可见光,将NO光催化氧化为NO3^-.但是由于自身的光生载流子复合率较高,光谱响应范围较窄等缺点,g-C3N4不能有效的光催化去除空气中持续流动的低浓度NO,限制了其在光催化领域中的实际应用.因此,有必要合成出高催化活性、高光响应范围的S型复合光催化剂来克服以上光催化材料的不足.为此,我们利用超声辅助法制备了一系列的S型Sb2WO6/g-C3N4复合光催化剂,呈现出优异的光催化活性:与其纯组分相比,所制备的15-Sb2WO6/g-C3N4复合光催化剂在可见光下照射30 min,可去除68%以上的持续流动的NO(初始浓度400 ppb),且五次循环实验后,Sb2WO6/g-C3N4复合光催化剂仍然具备良好的光催化活性和稳定性.透射电子显微镜结果清楚地表明,Sb2WO6颗粒已成功地均匀地负载到g-C3N4纳米片表面.紫外可见漫反射光谱的结果表明,Sb2WO6和g-C3N4的复合可以有效地提高对可见光的吸收能力.与纯g-C3N4样品相比,复合样的吸收带边具有明显的红移.光致发光光谱结果表明,在Sb2WO6/g-C3N4复合半导体中,光生载流子的复合受到抑制.光电流与电阻抗分析可知,与纯Sb2WO6和g-C3N4相比较,在15-Sb2WO6/g-C3N4复合光催化剂中的光生载流子的迁移速率和分离效率较高.通过对样品的能带结构分析并已有参考文献,我们认为Sb2WO6和g-C3N4的接触边界形成了S型异质结,使光生载流子的转移速率更快,改善了光生电子-空穴对分离,而且增强可见光的利用效率,从而提高了光催化性能.自由基捕获实验结果证实,?O2^-主导了Sb2WO6/g-C3N4复合光催化剂去除NO反应,h^+也在一定程度上参与了光催化氧化NO的反应.通过原位红外光谱技术研究了Sb2WO6/g-C3N4光催化NO氧化的反应机理,研究发现,Sb2WO6/g-C3N4复合光催化剂光催化去除是氧诱导的反应.具体反应机理是在可见光的驱动下,光催化剂表面的光生电子会与被吸附的O2反应生成?O2^-,并与光生h^+一起,共同将低浓度的NO光催化氧化为亚硝酸盐或硝酸盐.该研究有助于深入研究光催化氧化NO机理,并为设计高效光催化剂用于光催化氧化ppb级NO提供了一种极具前景的策略.     

高效可见光响应Zn_(0.11)Sn_(0.12)Cd_(0.84)S_(1.12)/g-C_3N_4异质结光催化剂的制备及性能

以双氰胺、醋酸锌、四氯化锡、醋酸镉和硫化钠为原料,采用水热法制备了三元金属复合硫化物Zn_(0.11)Sn_(0.12)Cd_(0.84)S_(1.12)(ZnSnCdS)及一系列异质结催化剂ZnSnCdS/g-C_3N_4.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、紫外-可见光谱仪(UV-Vis)、傅里叶变换红外光谱仪(FTIR)、电感耦合等离子体-质谱仪(ICP-MS)、荧光光谱仪(PL)和X射线光电子能谱仪(XPS)等对催化剂进行了表征.结果表明,ZnSnCdS与g-C_3N_4之间以C—S键紧密结合,构筑了异质结,促进了界面电荷迁移,抑制了光生电子-空穴对的复合.可见光下降解染料罗丹明B(RhB)的结果表明,ZnSnCdS/g-C_3N_4异质结催化剂的光催化性能与单纯g-C_3N_4,ZnSnCdS及双组分硫化物/g-C3N4异质结催化剂相比均有大幅度提高,ZnSnCdS与g-C3N4质量比为4∶1时异质结催化剂表现出最大的速率常数(0.1508 min-1),是单纯g-C_3N_4和ZnSnCdS的32.3倍和4.9倍.其它三元金属复合硫化物如ZnMoCdS,MoNiCdS和NiSnCdS与g-C_3N_4之间也能有效形成异质结,促进电子-空穴对的分离和催化性能的提升.     

化学镀法制备CoP量子点修饰g-C3N4用于光催化产氢（英文）

光催化分解水制氢被认为是解决当前能源危机和环境污染问题的重要途径之一.在众多光催化剂中,石墨相氮化碳(g-C3N4)因其具有高的热稳定性、高的化学稳定性、合适的能带位置以及成本低廉等优点,受到光催化领域研究者的广泛关注,成为研究热点.然而,由于g-C3N4的禁带宽度较大(Eg=2.7 eV),导致其对可见光的响应较差,而且光生电子-空穴对在其中易于复合,从而导致其光催化产氢活性较低.已有研究表明,助催化剂可以有效地促进催化剂中光生载流子的分离和传输,从而提高光催化剂的光催化活性和氢气的产生速率.目前使用最广泛的助催化剂多为贵金属(Au,Ag,Pt和Pd等),然而贵金属储量低、成本高,极大地限制了其实际应用.因而,开发适用于光催化水分解制氢的非贵金属助催化剂成为该领域的研究热点.其中,用非贵金属助催化剂修饰g-C3N4制备高效光催化剂分解水制氢技术引起了人们极大的兴趣.过渡金属磷化物(FeP,CoP,CuP,NiP等)是一种有效的光催化辅助催化剂.然而,这些金属磷化物的合成通常使用有毒的有机磷化合物和白磷或涉高温煅烧.特别是在传统水热法制备金属磷化物过程中会释放大量氢气,导致容器内压力过高,造成较大的安全问题.据报道,在这些磷化物中,磷化钴由于其合适的能带结构和较高的导电性,作为光催化分解水助催化剂受到了广泛关注.然而,截至目前,关于磷化钴作为助催化剂用于光催化的实用技术报道很少,特别是在温和条件下制备磷化钴修饰的g-C3N4复合光催化剂的研究还有待进行.本文研究了以CoP作为助催化剂来改进g-C3N4(制备g-C3N4/CoP),并用于光催化水裂解制氢气.复合光催化剂g-C3N4/CoP经由两步反应合成.第一步采用尿素热分解法制备g-C3N4,第二步通过化学镀法将CoP修饰在g-C3N4表面.采用XRD,TEM,UV-DRS和XPS等手段表征了g-C3N4/CoP光催剂的性质.结果表明,CoP以量子点(QDs)形式均匀分布在g-C3N4表面,显著提高了g-C3N4的光催化活性.不同CoP负载量的样品中,g-C3N4/CoP-4%表现出优异的光催化活性,H2生成速率为936μmol g^-1 h^-1,甚至高于4%Pt负载的g-C3N4(H2的生成速率仅为665μmol g^-1 h^-1).从紫外可见光谱上看,g-C3N4在451 nm达到吸收波长上限,但与CoP复合后,g-C3N4/CoP-4%的吸收波长上限延展到497 nm.此外,光致发光和光电流测试结果证实,将CoP量子点负载到g-C3N4上不仅可以降低光生电荷-空穴对的复合,而且可以改善光生e--h+对的转移,从而提高光催化剂的产氢性能.这项工作为开发高效的非贵金属助催化剂修饰g-C3N4的技术提供了一个可行策略,所制材料在光催化制氢领域显示出潜在的应用前景.     

Flower-like shaped Bi12TiO20/g-C3N4 heterojunction for effective elimination of organic pollutants: Preparation,characterization, and mechanism study

Flower-like shaped Bi₁₂TiO₂₀ (Bismuth Titanate)/g-C₃N₄ (graphite-like carbon nitride) heterojunction was prepared through hydrothermal and sonification methods for the degradation of organic pollutants by visible-light irradiation. The preparation process, chemical structures, and the mechanism of photocatalytic enhancement of the heterostructures were studied systematically. Under visible-light irradiation, the novel flower-like shaped Bi₁₂TiO₂₀/g-C₃N₄ heterojunction demonstrates prominent activities for the degradation of rhodamine B and p-nitrophenol, with the introduction of flower-like shaped Bi₁₂TiO₂₀ into g-C₃N₄ composites greatly increasing the activity of pure g-C₃N₄. This activity enhancement for the heterojunction could be mainly attributed to its low recombination speed of electron–hole pairs, high adsorption ability of organic pollutants, and better optical absorption ability. Moreover, in the visible-light system of Bi₁₂TiO₂₀/g-C₃N₄, ^•OH also contributed to the degradation of pollutants, which may explain the enhanced photocatalytic activity after the introduction of Bi₁₂TiO_20, as ^•OH is inactive in pure g-C₃N₄. Furthermore, 10 wt.% Bi₁₂TiO₂₀/g-C₃N₄ showed not only high activity but also good stability for degradation of aqueous organic pollutants, implying potential applications prospect.     

Photocatalytic Degradation of 4-Chlorophenol by Gd-Doped β-Bi2O3 Under Visible Light Irradiation

Chlorophenols are known as persistent organic pollutants.Therefore,research on the removal of chlorophenols has attracted widespread attention.Hereto,the photocatalytic degradation of 4-chlorophenol by Gd-doped β-Bi2O3 under visible light irradiation was studied.The results showed that Gd-doped β-Bi2O3 materials are efficient catalysts for the photocatalytic degradation of chlorophenols,and 2%(atomic traction)Gd-doped β-Bi2O3 exhibits the highest photocatalytic activity for 4-chlorophenol degradation,because doping an appropriate amount of Gd^3+ions can effectively reduce the recombination rate of the photogenerated e^-/h^+pairs and then enhance the photocatalytic performance.When the reaction was carried out at 25 ℃ for 6 h using the 2% Gd-doped/β-Bi2O3 micro/nano materials of 200 mg and at air flow rate of 40 mL/min,the degradation rate of 4-chlorophenol reached 92.3%.Additionally based on the analysis of the products,it was speculated that the dominant photocatalytic degradation mechanism of 4-chlorophenol by Gd-doped β-Bi2O3 under visible light irradiation is an oxidative process involving an attack by the hydroxyl radical.     

基于g-C3N4的Z型光催化体系研究进展

导电聚合物型光催化材料g-C₃N₄有着独特的电子结构、稳定的化学性能和显著的可见光催化活性。基于g-C₃N₄的Z型光催化体系(Z-g-C₃N₄)的催化效率高、电子-空穴复合率低而备受关注,在光催化领域展现出了巨大的应用潜力。本文阐述了Z-g-C₃N₄型光催化反应体系的作用机理,综述了Z-g-C₃N₄在光催化领域的研究进展,介绍了Z-g-C₃N₄在产氢、转化CO₂、降解有机物等光催化领域的应用,讨论了pH值、导电介质等因素对Z-g-C₃N₄光催化性能的影响。最后指出了Z-g-C₃N₄光催化体系在研究过程中面临的问题和研究方向。