基于二氧化钛光催化剂生物质转化制备氢气和化学品的研究进展

随着化石能源的枯竭和环境问题的日益严重,发展可再生资源变得越来越重要.太阳能和生物质是自然界中的两大可再生资源.利用太阳能转化生物质制备H2和化学品可以缓解对化石能源的依赖,是解决能源和环境问题的途径之一.本文作者概述了基于TiO2催化剂的光催化生物质制备H2和化学品的研究进展;着重介绍了甲醇、乙醇、甘油和葡萄糖的光催化反应选择性问题和机理研究,分析了存在的问题和可能的解决措施,并就其发展趋势进行了展望.     

NiO_x/介孔杭锦2~#土的制备及其对苯羟基化光催化性能研究

以沉积沉淀法制备Ni Ox/介孔杭锦2#土催化剂,通过X射线粉末衍射,比表面积及孔结构分析,固体紫外可见漫反射等手段对催化剂进行了表征.以H2O2为氧化剂,在汞灯照射下,研究其对光催化苯直接羟基化反应的催化性能,并探讨了镍的负载量,光源等因素对苯直接氧化制苯酚反应的影响.结果表明,随着镍含量的增加,苯酚的选择性和产率先增大后减小.在优化的反应条件下,苯酚的选择性和产率分别为93%和为56%.     

Construction,PPy loading and photocatalytic performance of a polyoxometalate-templated metallacycle compound

A polyoxometalate-templated metallacycle compound, [Ag₆trz₆][H₃PMo₁₂O₄₀]₂·6H₂O (trz = 1,2,3-triazole), has been isolated and structurally characterized. The compound represents the first example of a trigonal antiprism based metal-organic framework (MOFs) with complicated Zr₆Br₁₂ type topology, in which the trigonal antiprisms as building blocks are constructed by the Ag₆trz₆ space polygons and the bifunctional POMs (both as template and building block). In addition, to improve the photocatalytic activity of polyoxometalate-templated metallacycle compound, polypyrrole was loaded on its surface through a chemical oxidation polymerization process in situ. Finally, the photocatalytic activity of [Ag₆trz₆][H₃PMo₁₂O₄₀]₂ and PPy@[Ag₆trz₆][H₃PMo₁₂O₄₀]₂ under visible light was explored, and the results demonstrate that the PPy loading on the surface of POMs-based hybrid compound is feasible to improve their photocatalytic performance.     

Highly Efficient Ag3PO4/g-C3N4 Z-Scheme Photocatalyst for Its Enhanced Photocatalytic Performance in Degradation of Rhodamine B and Phenol

Ag₃PO₄/g-C₃N₄ heterojunctions, with different g-C₃N₄ dosages, were synthesized using an in situ deposition method, and the photocatalytic performance of g-C₃N₄/Ag₃PO₄ heterojunctions was studied under simulated sunlight conditions. The results revealed that Ag₃PO₄/g-C₃N₄ exhibited excellent photocatalytic degradation activity for rhodamine B (Rh B) and phenol under the same light conditions. When the dosage of g-C₃N₄ was 30%, the degradation rate of Rh B at 9 min and phenol at 30 min was found to be 99.4% and 97.3%, respectively. After five cycles of the degradation experiment for Rh B, g-C₃N₄/Ag₃PO₄ still demonstrated stable photodegradation characteristics. The significant improvement in the photocatalytic activity and stability of g-C₃N₄/Ag₃PO₄ was attributed to the rapid charge separation between g-C₃N₄ and Ag₃PO₄ during the Z-scheme charge transfer and recombination process.     

Progress in Visible Light‐Induced Difluroalkylation of Olefins

The incorporation of difluoromethylated (CF₂) moiety into potentially useful parent molecules lead to significant changes in metabolic stability, lipophilicity, and solubility of the molecules. Over the past several years, with the advent of new difluoromethylating reagents, great progress has been made in the development of a protocol for the direct incorporation of the CF₂H group into organic molecules. Among them, difluroalkylation induced by visible light has emerged as an efficient strategy over the past few years. In particular, this protocol provides a more sustainable alternative to other traditional radical‐triggered reactions in terms of environment, energy, step‐economy, health, and safety. The present review mainly focuses on the development of the photocatalytic difluoroalkylation to olefinic moiety using transition‐metal complexes, organic dyes as the photocatalyst; and some organic compounds as a medium of photocatalysis.     

Synthesis and properties of Au/ZnO nanorods as a plasmonic photocatalyst

It is of great interest to develop plasmonic photocatalysts with high activity and stability recently. In this paper, Au/ZnO nanorods were synthesized via a facile hydrothermal method and used as photocatalysts for methyl orange dye degradation. The results revealed an interesting phenomenon that photocorrosion cracks were produced specially along the c-axis of pure ZnO nanorods for five cycles photodegradation experiments under UV–vis. light irradiation, while Au nanoparticles surface modification can effectively inhibit the occurrence of photocorrosion and improve its photocatalytic activity. The formation of photocorrossion cracks along the c-axis of pure ZnO nanorods verifies the photogenerated charges may follow the route that electrons migrate to Zn-terminated (0001) plane and holes to O-terminated $(000\stackrel{-}{1})$ plane. SPR effect of Au nanoparticles enhances the light absorption ability and the electrons capture ability of Au/ZnO nanorods. Moreover, the surface adsorbed hydroxyl groups content is also increased due to Au nanoparticles modification. As Au nanoparticles can capture photogenerated electrons and hydroxyl groups are the favorable holes scavenger, the charges generation and separation in photocatalysis are strengthened. Especially, the charges separation path in Au/ZnO nanorods have changed, thus inhibiting the occurrence of photocorrosion along the c-axis of ZnO nanorods and improving the photocatalytic activity.     

Theoretical progress on direct Z-scheme photocatalysis of two-dimensional heterostructures

Two-dimensional (2D) materials, due to its excellent mechanical, unique electrical and optical properties, have become hot materials in the field of photocatalysis. Especially, 2D heterostructures can well inhibit the recombination of photogenerated electrons and holes in photocatalysis because of its special energy band structures and carrier transport characteristics, which are conducive to enhancing photoenergy conversion capacity and improving oxidation and reduction ability, so as to purify pollutants and store energy. In this minireview, we summarize recent theoretical progress in direct Z-scheme photocatalysis of 2D heterostructures, focusing on physical mechanism and improving catalytic efficiency. Current challenges and prospects for 2D direct Z-scheme photocatalysts are discussed as well.     

Template‐free synthesis of hierarchical zinc oxide with improved photocatalytic properties

Novel hierarchical nano materials possess tremendous latent force in many applications. In this paper, hierarchical flower‐like, spherical and bowl‐like zinc oxide was successfully synthesized by altering solvent ratio (absolute ethanol and diethylene glycol) via a simple and template‐free solvothermal synthetic route. The solvent ratio also plays a vital role in deciding the structure, crystalline, band gap energy and specific surface area of the as‐synthesized samples. The preparation mechanism of ZnO in mixed alcohols was discussed. The obtained samples were characterized by energy dispersive spectroscopy(EDS), X‐ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), N2 adsorption‐desorption, UV–vis diffuse reflectance spectroscopy (DRS). Photocatalytic activity of the as‐prepared ZnO nanocrystals was evaluated by the degradation of MB under UV irradiation. Among, the most effective photocatalyst was synthesized when the diethylene glycol was 10 ml.     

Bi4O5Br2/Ti3C2-Ru复合光催化剂的合成及其对磺胺甲噁唑药物废水降解性能研究

Bi_xO_yBr_z光催化剂在有机药物废水处理领域有着非常广阔的潜在应用价值,但光生电子-空穴对的快速复合限制了其应用。本文选用具有优良电子传递性能的Ti₃C₂作为助催化剂,首先利用Ti₃C₂表面丰富的Ti空位缺陷和高还原能力,制备了Ti₃C₂-Ru助催化剂,接着利用Ti₃C₂表面官能团与Bi³⁺的离子键合力实现了Bi₄O₅Br₂在Ti₃C₂-Ru表面的原位生长,得到Bi₄O₅Br₂/Ti₃C₂-Ru复合光催化剂,从而实现了电子由Bi₄O₅Br₂到Ti₃C₂再到反应活性位点Ru的定向传递,最终使催化剂具有较高的光生载流子分离率和较低的界面电荷转移阻力,有效抑制了光生电子-空穴对的复合。同时以磺胺甲噁唑(SMX)为模拟药物污染物进行了光催化性能测试,结果表明所制备的Bi₄O₅Br₂/Ti₃C₂-Ru复合光催化剂展示出了优异的光催化降解SMX性能,在可见光下照射75 min,SMX的降解率达到95.1%,相较于纯的Bi₄O₅Br₂和Bi₄O₅Br₂/Ti₃C₂催化剂,其降解率分别提升了36.9个百分点和25.3个百分点。最后基于自由基捕获实验和催化剂能带结构分析提出了所制催化剂的降解机理。研究结果可为构建具有药物废水净化功能的光催化剂提供设计思路。     

Tuning band alignment and optical properties of 2D van der Waals heterostructure via ferroelectric polarization switching

Favourable band alignment and excellent visible light response are vital for photochemical water splitting. In this work, we have theoretically investigated how ferroelectric polarization and its reversibility in direction can be utilized to modulate the band alignment and optical absorption properties. For this objective, 2D van der Waals heterostructures (HTSs) are constructed by interfacing monolayer MoS₂ with ferroelectric In2Se3. We find the switch of polarization direction has dramatically changed the band alignment, thus facilitating different type of reactions. In In₂Se₃/MoS₂/In₂Se₃ heterostructures, one polarization direction supports hydrogen evolution reaction and another polarization direction can favour oxygen evolution reaction. These can be used to create tuneable photocatalyst materials where water reduction reactions can be selectively controlled by polarization switching. The modulation of band alignment is attributed to the shift of reaction potential caused by spontaneous polarization. Additionally, the formed type-II van der Waals HTSs also significantly improve charge separation and enhance the optical absorption in the visible and infrared regions. Our results pave a way in the design of van der Waals HTSs for water splitting using ferroelectric materials.