ZnO的改性及其光催化性能的研究进展

氧化锌(ZnO)是一种重要的半导体光催化剂，具有光催化活性高、价格低廉、化学稳定性好和无毒无害等优点.但是其自身存在一定的缺陷，国内外学者曾采用多种方法对其修饰改性.本文主要综述了ZnO修饰改性的方法，包括掺杂金属与非金属、贵金属沉积、构建异质结及耦合碳材料.其次，综述了复合材料的光催化性能，最后对ZnO在光催化方面的发展前景进行了展望.     

金属卤化物钙钛矿光催化的研究进展

太阳能驱动光催化反应降解污染物、制备化学燃料或其他高附加值产品是绿色化学和可再生能源研究的重要方向.近年来,在传统的金属氧化物半导体材料之外,金属卤化物钙钛矿类化合物凭借其优异的光电特性也被逐步应用于高效光催化反应中.这篇文章综述了以铅卤钙钛矿为主的金属卤化物钙钛矿材料近年来在光催化领域的研究进展,总结了金属卤化物钙钛矿材料在光（电）催化产氢、CO₂还原反应和有机物高附加值转化反应中的应用与反应机制及其关键挑战,最后展望了高效稳定的金属卤化物钙钛矿光催化剂的发展方向和前景.     

悬浮体系中的半导体光催化及其应用

最近十多年来,在半导体界面上进行的光能化学转化——半导体光催化,成了催化学科中的活跃研究领域之一。科学工作者们从太阳能利用等不同的角度出发,对各种类型的半导体光催化反应进行了广泛深入的研究。迄今已     

光催化分解水制氢用二元半导体光催化剂

光催化分解水制氢被认为是解决能源问题和环境问题的有效方法,但目前的光催化效率仍然较低,结合使用2种半导体物质是提高光催化活性的一种有效途径。本文分两种类型阐述了已报道的用于光催化分解水制氢反应的二元半导体体系。一种为将2种半导体复合于一体,另一种为将2种半导体分散加入到光催化反应液中的Z型体系。基于肖特基模型探讨了2种半导体复合于一体的二元体系的光催化作用机制,指出p型半导体和n型半导体复合制得的光催化剂更能很好地发挥各半导体的光催化氧化性能和光催化还原性能。分析了Z型体系的优点和缺点,指出对于Z型体系的放氢催化剂和放氧催化剂也可以分别再进行二元复合改性,以抑制光激发载流子的复合,提高整个体系的光催化效率。     

半导体光催化研究进展与展望

评述了目前半导体光催化在国内外的研究概况,并对存在的问题和未来的发展动向进行简要分析.列举了近30年来关于光催化研究的部分成果,内容涉及光催化剂的制备(包括新催化剂的开发, TiO2、 ZnO、 CdS等光催化剂的各种改性或修饰)、光催化作用机理研究、光催化技术的工程化、光催化技术的各种应用研究和产品开发等等从基础到应用研究的各个方面.总体上来看,半导体光催化基本上是一个没有选择性的化学过程,所以再进行大量的不同反应物的光催化活性的评价研究意义已不是很显著,认为未来的半导体光催化研究应该集中在机理的深刻认识、光响应范围宽和量子效率高的催化剂制备、半导体光催化技术工程化及新型光催化产品开发方面.     

光催化技术在降解有机染料污染物方面的应用

光催化技术是一种新兴的高效节能现代污水处理技术,本文从半导体光催化技术研究现状、反应机理、反应动力学、光催化技术发展及其存在的问题等方面对半导体光催化技术在降解常见有机染料方面的应用加以综述.     

碳纳米管/半导体复合材料光催化研究进展

碳纳米管具有良好的机械性能和导电性、高化学稳定性、大表面积以及独特的一维结构,与半导体光催化剂结合能够增强催化剂的吸附能力、提高光催化效率、扩展光响应范围,而且有利于回收催化剂,极大地提高了半导体光催化剂的综合性能。本文首先分析了半导体光催化剂和碳纳米管的特点,总结了碳纳米管增强半导体光催化的机理,然后分别从复合材料制备方法、复合半导体种类和典型的应用三个不同角度,归纳总结了近年来碳纳米管/半导体复合材料光催化的研究进展,最后对其发展趋势作了展望。     

全固态Z-Scheme光催化材料应用于二氧化碳还原和光催化分解水研究进展

由两种不同的半导体催化剂和电子传输介质建立的Z-Scheme光催化体系,通过在可见光照射下分别在两种半导体催化剂上进行氧化反应和还原反应,实现两步法光催化分解水和二氧化碳还原.相较于离子型Z-Scheme光催化体系,全固态Z-Scheme光催化体系具有适用范围广、无副反应、光源利用率高等特性,具有更加广阔的应用前景.在此,我们简述了Z-Scheme光催化体系的反应机理,综述了全固态Z-Scheme光催化体系在光催化分解水和光催化还原CO₂领域的应用,并对未来全固态Z-Scheme光催化体系的发展进行了展望.     

一种新的光催化氧化体系用于化学需氧量的测定研究

基于KMnO₄能获得光生电子从而提高半导体光催化氧化能力的原理,建立了一种用纳米ZnO-KMnO₄协同体系光催化测定化学需氧量(COD)的新方法,探讨了催化氧化测定COD的机理,考察了测定COD的最佳反应条件.COD值浓度在1.5～10mg/L范围内与信号呈良好的线性关系,检测限为0.5mg/L.用本方法测定实际水样,结果和标准高锰酸盐指数法(COD_Mn法)相符.     

光诱导双助催化剂在半导体表面的自发形成（英文）

半导体光催化体系的助催化剂在光生电荷分离和表面催化反应过程中扮演着重要的角色.然而,在反应条件下助催化剂的化学态是否发生改变尚不清楚.本文以钽酸钠为模型光催化剂,系统地研究了镍基助催化剂在光催化分解水反应中的化学态.结果发现,在光诱导条件下半导体钽酸钠单晶表面自发形成了金属镍和氧化镍双助催化剂.首先用传统的水热法合成只暴露单一晶面的六面体钽酸钠半导体单晶光催化剂和暴露不等同晶面的二十六面体钽酸钠半导体单晶光催化剂.原位光沉积结果显示,暴露不同晶面的二十六面体钽酸钠半导体单晶光催化剂存在晶面间的电荷分离现象,进一步利用该现象可以确定不同催化活性位上镍基助催化剂的作用.XPS结果显示,半导体钽酸钠单晶表面的镍基助催化剂存在的不同价态.高分辨透射电镜结果表明,不同晶面上的镍基助催化剂具有不同的形貌,并且通过晶格衍射条纹的对比确认了不同镍基助催化剂物种的归属和作用.将表面浸渍氧化镍的二十六面体钽酸钠半导体光催化剂用于全分解水测试发现,反应开始阶段H_2:O_2比值小于2:1,说明部分光生电子被消耗掉,用于还原氧化镍,生成了金属镍.将表面还原的金属镍光催化剂进行全分解水测试发现,反应开始阶段H_2:O_2比值大于2:1,说明部分光生空穴被消耗掉,用于氧化金属镍,生成了氧化镍,金属镍和氧化镍最终在反应的过程中达到了平衡.金属镍担载在{001}晶面上,起着还原助催化剂的作用,参与质子还原,释放出H_2;氧化镍担载在其他晶面上,扮演着氧化助催化剂,参与水的氧化,释放出O_2;金属镍和氧化镍共同促进了光催化全分解水反应,使反应活性达到了最高.这种双助催化剂的自发形成现象不仅存在于二十六面体钽酸钠单晶半导体表面,在六面体钽酸钠单晶半导体表面也同样存在,是一个普适性的现象.在六面体钽酸钠半导体单晶光催化剂表面同样可以发现不同形貌的镍基助催化剂,分别归属于金属镍和氧化镍.本文说明了助催化剂的化学态在光催化反应的条件下是可以发生改变的,并且光生电荷可以在半导体表面诱导双助催化剂的自发形成.     

Optimizing electronic structure and charge transport of sulfur/potassium co‐doped graphitic carbon nitride with efficient photocatalytic hydrogen evolution performance

Recently, graphitic carbon nitride (CN) has been widely investigated for solar energy conversion through water splitting, but its low photocatalytic activity needs to be further improved and optimized. Herein, S/K co‐doped CN photocatalysts have been fabricated by condensation of thiourea and dithiooxamide followed by post‐treatment in molten salt. As evidenced by XRD patterns and UV–vis DRS plots, the engineering crystalline and electronic structure of all as‐prepared samples have been explored through tailoring the mass ratio of thiourea and dithiooxamide as well as ratio of molten salt/the precursor. After optimization, the as‐prepared S/K co‐doped CN photocatalysts with needle‐like nanorods structure exhibit excellent hydrogen evolution rate of 1962.10 μmol^?1 g^?1 h^?1. While its photocatalytic activity is lower than that of pure CN by molten salt treatment (K‐doped CN) (2066.40 μmol^?1 g^?1 h^?1), which results from that the K content of S/K co‐doped CN photocatalyst is lower than that of K‐doped CN. Moreover, compared with K‐doped CN, S/K co‐doped CN photocatalyst possesses higher photocatalytic performance when irradiated by a light source (λ > 520 nm). This might be ascribed to the fact that the introduction of sulfur can expand light absorption region (λ > 520 nm), whereas K cannot improve light absorption of CN in this wavelength region. Furthermore, DFT calculation reveals that both S and K atoms can offer more electrons to band gap, leading to the formation of metallic‐character band structure. In addition, K atom can intercalate in the interlayer of CN and bridge the adjacent two layers, leading to the formation of charge delivery channels. These results demonstrate that S/K co‐doped CN photocatalysts facilitate the separation and transport of photogenerated charge carries, resulting in the efficient photocatalytic activity for hydrogen evolution. Besides, a competition between sulfur and potassium atom during the synthesis process is also discussed in details.     

Hollow Carbon Sphere-Modified Graphitic Carbon Nitride for Efficient Photocatalytic H2 Production

A novel hybrid photocatalyst composed of hollow carbon nanospheres (NCS) and graphitic carbon nitride (CN) curly nanosheets has been prepared by the calcination of a NCS precursor and freeze-dried urea. The optimized photocatalyst exhibits an efficient photocatalytic performance under visible light irradiation with a highest H₂ generation rate of 3612.3 μmol g⁻¹ h⁻¹, leading to an apparent quantum yield of 10.04 % at 420 nm, five times higher than the widely reported benchmark photocatalyst CN (2.01 % AQY). The materials characterization shows that NCS-modified CN curly nanosheets can promote photoelectron transfer and suppress charge recombination through their special coupling interface and NCS as an electron acceptor, which significantly improves the photocatalytic efficiency. Thus, this study provides an efficient strategy for the design of highly efficient photocatalyst, particularly suitable for a totally metal-free photocatalytic system.     

Utilization of Environmentally Benign Dicyandiamide as a Precursor for the Synthesis of Ordered Mesoporous Carbon Nitride and its Application in Base‐Catalyzed Reactions

Assisted by a new dissolution procedure, dicyandiamide (DCDA), an environmentally benign and cheap precursor, has been employed for the synthesis of mesoporous carbon nitride (CN) materials through a nanocasting approach. The synthesized mesoporous materials possessed high specific surface areas (269–715 m² g^?1) with narrow pore‐size distributions (about 5 nm) and faithfully replicated the mesostructures of the SBA‐15 and FDU‐12 templates. Several characterization techniques, including XRD, SAXS, TEM, Raman and FTIR spectroscopy, XPS, and CO₂‐TPD, were used to analyze the physicochemical properties of these materials and the results showed that the mesoporous CND materials had graphitic‐like structures and consisted of CN heterocycles, as well as amino groups. In a series of Knoevenagel condensation reactions, as exemplified by the reaction of various aldehydes and nitriles, these mesoporous CND materials demonstrated high and stable catalytic activities, owing to an abundance of basic sites.     

Photocatalytic performance of BiFeO3 based on MOFs precursor

BiFeO₃ (BFO) is considered to be a potential visible light photocatalytic material for organic degradation due to its narrow band gap. In this work, the BFO with smaller band gap and better photocatalytic performance was prepared by thermal decomposition of we prepared smaller band gap and better photocatalytic performance BFO by thermal decomposition of MOFs precursor Bi[Fe (CN)₆]·5H₂O. Among them, BFO‐0.5 has the best photocatalytic activity, which the photocatalytic degradation rate of methyl orange (MO) aqueous solution is 98.1% within 60 minutes. The photocatalytic activity is almost unchanged after four cycles of use. The enhanced photocatalytic activity of BFO could be attributed to the enhanced optical absorption and smaller particles. It may be conducive to design more efficient photocatalysts for photocatalytic degradation of organic dyes.     

多孔TiO2薄膜自洁净玻璃的亲水性和光催化活性

亲水性多孔TiO₂薄膜自洁净玻璃以含聚乙二醇的钛醇盐溶胶前驱体中通过浸渍提拉法制备;随着前驱物中聚乙二醇加入量的增加,多孔TiO₂薄膜表面的羟基含量也增加,薄膜表面的亲水性增强,水与薄膜表面的接触角下降为0°.该亲水性多孔TiO₂薄膜自洁净玻璃具有明显的自洁净和易清洗功能.紫外-可见光透过光谱分析表明,随着TiO₂薄膜中孔径的增大,光的散射增强,透光率减小.该TiO₂镀膜玻璃对于紫外线具有吸收作用.甲基橙水溶液的光催化降解实验表明,在TiO₂薄膜中引入适当大小的微孔可显著增强薄膜的光催化活性,但当孔径接近400nm时,薄膜的光催化活性减弱.     

Realizing high-efficiency carrier separation in 3D hierarchical carbon nitride nanosheets via intramolecular donor-acceptor motifs strategy

The insufficient visible light responsive region and fast charge recombination probability are still the key obstacles for designing high-performance photocatalytic system. Herein, a “One Stone, Two Birds” strategy was reported in three-dimensional (3D) hierarchical graphitic carbon nitride (g-C₃N₄) nanosheet with intramolecular donor-acceptor (D-A) motifs (3D CN) photocatalyst, which solved two urgent problems simultaneously. The 3D hierarchical nanosheets structure endowed 3D CN with abundantly exposed reaction active sites and cross-plane diffusion channels. The formation of internal D-A system facilitated the light absorption and accelerated the transfer and separation of charge carriers. Furthermore, the introducing of D-A motifs optimized the bandgap of g-C₃N₄ and negative-shifted conduction band position. The as-prepared 3D CN showed excellent visible-light photocatalytic H₂ performance, with H₂ evolution rate of 2521.2 μmol h^?1/g, which was six times higher than the pristine CN. This outstanding performance was ascribed to the synergistic effect of 3D hierarchical nanosheets structure and intramolecular D-A motifs. This current work provides a novel insight to design and construct of 3D hierarchical CN nanostructures with D-A motifs simultaneously, which can be further promising applications for clean and sustainable energy conversion.     

多孔纳米片状石墨相氮化碳的制备及其可见光催化

以三聚氰胺和硫脲为前驱体,通过简易的氧气刻蚀制备了多孔纳米片状氮化碳。相比于三聚氰胺制备的薄片状氮化碳（MCNS）,以硫脲制备的多孔纳米片状的g-C₃N₄（TCNS）片层更薄,其单片厚度约为30 nm,且TCNS的层状结构明显,能带隙约为3.03 eV,高于石墨相氮化碳（2.77 eV）,更宽的禁带赋予载流子更强的氧化还原能力。较大的比表面积（114 m²·g^-1）可以提供更多的活性位点,同时纳米片状结构可以促进电子与空穴的有效分离和转移,且能有效地降低光生载流子的复合率,因而TCNS具有更高的光催化活性。     

多孔纳米片状石墨相氮化碳的制备及其可见光催化

以三聚氰胺和硫脲为前驱体,通过简易的氧气刻蚀制备了多孔纳米片状氮化碳。相比于三聚氰胺制备的薄片状氮化碳(MCNS),以硫脲制备的多孔纳米片状的g-C_3N_4(TCNS)片层更薄,其单片厚度约为30 nm,且TCNS的层状结构明显,能带隙约为3.03 eV,高于石墨相氮化碳(2.77 eV),更宽的禁带赋予载流子更强的氧化还原能力。较大的比表面积(114 m~2·g~(-1))可以提供更多的活性位点,同时纳米片状结构可以促进电子与空穴的有效分离和转移,且能有效地降低光生载流子的复合率,因而TCNS具有更高的光催化活性。     

Direct synthesis of nanoporous carbon nitride fibers using Al-based porous coordination polymers (Al-PCPs)

We report a new synthetic route for preparation of nanoporous carbon nitride fibers with graphitic carbon nitride polymers, by calcination of Al-based porous coordination polymers (Al-PCPs) with dicyandiamide (DCDA) under a nitrogen atmosphere.     

A facile soft-template synthesis of nitrogen doped mesoporous carbons for hydrogen sulfide removal

A series of nitrogen-doped mesoporous carbons (NMCs) were prepared using Pluronic F127 as a structure directing agent, phloroglucinol and formaldehyde as carbon precursor and dicyandiamide as nitrogen source. The obtained nitrogen-doped mesoporous carbons possess high nitrogen content of 6.37–19.28 wt%. Due to the feature of high nitrogen contents, NMCs show superior H₂S adsorption performance with breakthrough sulfur capacity of 0.48 mmol g^?1 at room temperature and ambient pressure. It is revealed that in addition to the nitrogen content, nitrogen configuration and porosity of the carbon materials also influence significantly their sulfur capacity. This work offers a facile strategy for the synthesis of porous carbon materials with excellent performance in the adsorptive removal of H₂S.