Mg/O共同修饰无定形氮化碳的独特电子结构增强光催化对四环素盐酸盐的降解（英文）

近年来,光催化技术被广泛应用于环境和能源领域.其中,g-C_3N_4因化学稳定性和热稳定性好、能带结构易调控而成为一种有前景的可见光光催化剂.然而,g-C_3N_4的电子-空穴对易复合,导致其不能充分利用太阳光,光催化效率并不理想.本文通过实验与理论结合的方法设计并制备了具有独特电子结构的Mg/O共同修饰的无定形氮化碳(记为MgO-CN),以30mg/L的四环素盐酸溶液(TC)作为目标污染物评价了其光催化性能.经X射线衍射、扫描电镜、透射电镜、N_2物理吸附、紫外-可见光谱等表征手段分析表明,MgO-CN样品(002)晶面的衍射峰强度随着MgO含量增加而减弱,CN趋向于无定形化.同时,MgO-CN样品的可见光吸收边带发生红移,呈现出更强的可见光吸收能力.此外,Mg原子和O原子共同修饰的独特电子结构可以通过C→O←Mg的电子传递路线在O原子周围产生局域电子,从而抑制电子-空穴的复合.光催化降解TC的实验结果表明,在可见光照射后,含有1.2 wt%MgO的复合样品MgO-CN-1.2具有最佳光催化活性,TC降解效率为82.0%,比g-C_3N_4的光催化效率(23.5%)高出58.5%,且光催化降解过程符合准一级动力学,MgO-CN-1.2的反应速率常数(0.01018 min~(–1))是g-C_3N_4(0.00205 min~(–1))的5倍.自由基捕获测试实验表明,g-C_3N_4和Mg O-CN-1.2样品均可以产生·O_2~–自由基和·OH自由基,但是Mg O-CN-1.2样品的·O_2~–和·OH信号更强.这是由于Mg O-CN-1.2样品可以吸收更大范围的可见光用于激发电子,同时结合理论计算证明,MgO-CN内部电子在O原子周围汇集,形成的电子定向传输通道对催化剂表面的电子-空穴复合有抑制作用,更加有利于电子的迁移而诱导O_2生成·O_2~–.由于Mg O-CN-1.2和g-C_3N_4的价带位置分别位于1.47和1.60 eV,此价带上的h~+不能与H_2O和OH~–直接反应生成·OH,而是由生成的·O_2~–再与H~+和e~–按照O_2→·O_2→H_2O_2→·OH的反应途径生成·OH.本文最后分析,MgO-CN复合物参与反应的主要活性物种为·O_2~–,·OH和h~+光催化降解污染物的反应机理.其中,·O_2~–对光催化降解TC的贡献最大,为最主要的活性物质.本文工作提供了一种新的策略来改变氮化碳的电子结构,对提高其催化性能具有积极意义.     

钨酸铋对四环素光催化降解性能

采用水热法制备了钨酸铋催化剂,以空气为氧化剂,四环素为底物,考察了制备催化剂时溶液的酸度、降解反应时不同光源、光强度和催化剂量对钨酸铋的光催化降解四环素性能的影响.结果表明,当制备钨酸铋催化剂溶液的pH为1时,催化降解效果较好;当催化剂与四环素的物质的量之比为0.3∶1时,光照时间100 min,光催化降解率达66%;以钨酸铋为催化剂,太阳光光催化降解性能优于红外光和紫外光,太阳光强度越强,催化降解效果越好.     

核黄素掺杂的新型石墨相氮化碳光催化剂的制备及其在四环素降解中的应用

针对g-C₃N₄有限的可见光吸收能力和容易复合的光生载流子限制其光催化性能发挥的问题,以尿素为前驱体,核黄素(RF）为掺杂试剂,通过一步热聚合制备了新型g-C₃N₄-RF光催化剂。系列表征测试(FT-IR,XRD,SEM,UV-vis DRS,PL）表明,该新型g-C₃N₄-RF光催化剂被成功制备,并具有优异的可见光吸收能力和有效的光生电子空穴对分离效率。光催化降解实验表明,该催化剂在可见光下对四环素抗生素具有优异的光催化降解性能。该研究为开发新型氮化碳光催化剂提供了新的思路,为抗生素污染物的高效去除提供了新的线索。

     

原位制备SrSb2O6/g-C3N4新型二维异质结用于可见光催化降解四环素的研究

本文采用高温固相原位制备新型二维SrSb2O6/g-C3N4异质结光催化复合材料,并将其用于可见光催化降解四环素.通过XRD和FT-IR谱对其结构进行表征.光催化降解实验表明,异质结复合材料较母体g-C3N4和SrSb2O6而言,光催化效率均得到了提升.其中,异质结样品SSO-CN-2对四环素溶液具有最优的光催化降解效...     

多孔双金属氧化物/碳复合光催化剂对四环素的高效光催化降解

本工作以金属有机框架材料UiO-67为载体,通过原位水解负载TiO_2,经焙烧后得到系列ZrxTi/C光催化剂。我们以四环素为典型抗生素在300 W氙灯光源下进行光降解研究,Zr_(0.3)Ti/C复合催化剂表现出优异的光催化效率,对于10 mg×L~(-1)四环素溶液,30 min可以降解98%。光降解速率常数分别是TiO_2、纯Ui O-67焙烧产物Zr-O-C的16倍和3.7倍。这得益于Zr_(0.3)Ti/C较大的比表面积,对四环素具有优异的吸附性能;同时具有能级匹配的Zr-O-C/TiO_2异质结构和高导电性碳材料共掺,有效提高了电子-空穴对的分离与迁移;机理研究表明光照下产生的超氧自由基(O_2·-)、羟基自由基(·OH)以及少量的空穴(h~+),共同促进了光催化降解四环素。本研究基于吸附和光催化协同作用原理,所提出的高比表面积、双金属活性的复合光催化材料的制备方法,对抗生素等环境污染物光降解治理方面有一定的指导作用。     

Mxene量子点增强磷掺杂氮化碳光催化降解污染物的性能

为了提高石墨相氮化碳的光催化性能,在合成磷掺杂氮化碳和Mxene量子点的基础上,构建具有0D-2D复合结构的Mxene/P-C₃N₄复合光催化剂。采用XRD、IR、TEM、AFM、BET、XPS、吸收光谱等技术对Mxene/P-C₃N₄的结构进行了分析,并详细评估了它们在可见光下光催化降解污水的性能,包括降解有机染料茜素红、降解抗生素盐酸四环素和还原重金属离子Cr(VI)。结果表明,磷的掺杂可以拓宽氮化碳的光吸收范围、降低其禁带宽度;Mxene量子点的负载不仅可以增加比表面积,还能有效抑制光生载流子的复合,促进光生载流子在界面处的分离和传输。磷和Mxene量子点的协同作用可以显著增强氮化碳的光催化性能。当磷的掺杂量为2%、Mxene量子点的负载量为5%时,得到的M5/PCN复合光催化剂表现出最好的光催化性能,60 min将初始浓度20 mg/L的茜素红降解94%,表观一级反应速率常数为0.0475 min^-1,分别是C₃N₄和P-C<...     

噻吩硫掺杂氮化碳促进n-π*电子跃迁增强光催化活性

光催化技术是一种绿色的化学技术,它可以利用取之不尽的太阳能来降解有毒污染物或者分解水产生氢气等.毋庸置疑,这项技术的核心是半导体光催化剂,在太阳光的照射下,半导体产生电子-空穴对,分别迁移至表面参与氧化还原反应.然而,半导体光催化剂中电子和空穴易快速复合以及其对太阳能中占主导的可见光利用率较低阻碍了其在实际中的应用.因...     

磁性Fe3O4/ZnO核壳材料的制备及降解四环素类抗生素

利用共沉淀及退火处理两步法,合成了具有核壳结构的磁性Fe3O4/ZnO纳米材料。采用X射线衍射仪、红外光谱仪、透射电子显微镜及振动样品磁强计(VSM)等技术对材料的组分、形貌及磁力性质进行表征,并以氙灯为光源,以四环素(TC)、强力霉素(DC)和盐酸土霉素(OTC)3种四环素类抗生素为降解目标,模拟测试样品在日光下的光催化活性,并通过改变Zn2+浓度,调节包覆结构从而得到最佳光催化效果。研究表明,ZnO包覆在Fe3O4表面并随Zn2+浓度增大逐渐形成尺寸在100 nm的锥形结构,当Zn2+浓度为0.5 mol/L时,样品对TC、DC和OTC的降解率最大,分别为85%、78%和64%。基于以上的研究显示,合成的磁性Fe3O4/ZnO核壳材料可应用去除水中抗生素,是一种具有高催化活性且能回收利用的新型复合光催化剂。     

高结晶氮化碳空心球的制备及其增强光催化产氢活性

石墨烯型氮化碳(g-C3N4)已经成为解决环境污染和能源危机问题的较为理想的光催化剂,但由于其较低的比表面积和较高的光生载流子重组效率而表现出较弱的光催化活性.因此,研究者们已经提出了许多策略,例如纳米结构设计,杂原子掺杂和增加结晶度,用来克服氮化碳的这些缺点,从而提高其光催化性能.其中,引起了较多关注的是增加g-C3...     

氮缺陷石墨相氮化碳的制备及其光催化降解环境有机污染物性能

通过在三聚氰胺热分解过程中加入NaHCO₃制备出具有氮缺陷的石墨相氮化碳（g-C₃N₄）,利用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、N₂吸附-脱附、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）和固体荧光光谱（PL）等方法对其进行表征,并在可见光（λ> 420nm）照射下,以水相中罗丹明B（RhB）的降解为模型反应,研究了该氮缺陷g-C₃N₄对有机污染物降解的光催化活性。结果表明,引入氮缺陷可以提高g-C₃N₄对可见光的吸收以及电子-空穴对的分离效率,进而提高g-C₃N₄的可见光催化活性。催化剂CNK0.005、CNK0.01和CNK0.05在30min内对RhB的降解率分别为79.8%、100.0%和87.6%;而在相同条件下,没有氮缺陷的g-C₃N₄对RhB的降解率仅为59.8%。     

二硫化钼量子点/还原氧化石墨烯复合材料的制备及其光催化降解有机染料、四环素和Cr（VI）

以钼酸钠、L-半胱氨酸和氧化石墨烯为原料,采用一锅溶剂热还原法制备了二硫化钼量子点/还原氧化石墨烯（MoS₂ QDs/rGO）复合材料,分别以罗丹明B、亚甲基蓝、四环素和Cr（VI）为目标污染物,研究了复合材料的可见光响应光催化降解性能。结果显示,MoS₂ QDs/rGO对两种染料和Cr（VI）的光催化降解率均可达97%以上,对四环素的光催化降解率为69%;循环使用10次,对目标染料的降解率均保持在90%以上。说明MoS₂ QDs/rGO具有良好的催化活性和稳定性。在降解体系中分别加入异丙醇、对苯醌和乙二胺四乙酸二钠捕获剂,结果显示,超氧自由基（?O₂^-）是MoS₂ QDs/rGO光催化反应的主要活性物种。     

纳米银/二维石墨相氮化碳/还原氧化石墨烯复合材料的制备及其光催化降解抗生素

为优化石墨相氮化碳(g-C₃N₄)光催化剂的结构,改善其对污染物的降解性能,本文以三聚氰胺为前驱体,通过高温煅烧和热氧化剥离制备了二维石墨相氮化碳(2D-C₃N₄),并用光还原法一步合成纳米银/二维石墨相氮化碳/还原氧化石墨烯(Ag/2D-C₃N₄/rGO)复合光催化剂。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)、光致发光光谱(PL)、X射线光电子能谱(XPS)、氮气吸附脱附等温曲线(BET)等对材料进行表征。 以头孢曲松钠为目标污染物,探究pH值、催化剂用量、头孢曲松钠初始浓度等因素对催化剂的吸附、降解性能的影响,并探究降解反应机理。 当pH=6.0,催化剂用量为0.3 g/L,头孢曲松钠初始浓度为10.0 mg/L时,复合材料对头孢曲松钠的降解率可达到89.1%。 催化剂的稳定性较强,具有实际应用价值,可用于处理含头孢类抗生素的废水。     

前驱体改性法制备薄层多孔富氨基的石墨相氮化碳用于光催化降解RhB和光催化制氢

半导体光催化是一种利用半导体将太阳能转换为高能化学能的绿色技术,在可再生清洁能源生产和污染物修复领域有着巨大的应用前景.石墨相氮化碳(g-C3N4)作为一种环境友好的非金属半导体,因其制备工艺简单、来源丰富、热稳定性和化学稳定性好、可见光吸收范围及特殊的电子性能而受到广泛关注.但一般常用氮源前驱体如二氰二胺、三聚氰胺等...     

非金属掺杂石墨相氮化碳光催化的研究进展与展望

Since Fujishima and Honda demonstrated the photoelectrochemical water splitting on TiO₂ photoanode and Pt counter electrode, photocatalysis has been considered as one of the most promising technologies for solving both the problems of environmental pollution and energy shortage. This process can effectively use solar energy, the most abundant energy resource on the earth, to drive various catalytic reactions, such as water splitting, CO₂ reduction, organic pollutant degradation, and organic synthesis, for energy generation and environmental purification. Except for the various metal-based semiconductors, such as metal oxides, metal sulfides, and metal oxynitrides, developed for photocatalysis, graphitic carbon nitride (g-C₃N₄) has attracted significant attention in the recent years because of its earth abundancy, non-toxicity, good stability, and relatively narrow band gap (2.7 eV) for visible light response. However, g-C₃N₄ suffers from insufficient absorption of visible light in the solar spectrum and rapid recombination of photogenerated electrons and holes, thus resulting in low photocatalytic activity. Until now, various strategies have been developed to enhance the photocatalytic activity of g-C₃N₄, including element doping, nanostructure and heterostructure design, and co-catalyst decoration. Among these methods, element doping has been found to be very effective for adjusting the unique electronic and molecular structures of g-C₃N₄, which could significantly expand the range of photoresponse under visible light and improve the charge separation. Especially, non-metal doping has been well investigated frequently to improve the photocatalytic activity of g-C₃N₄. The non-metal dopants commonly used for the doping of g-C₃N₄ include oxygen (O), phosphorus (P), sulfur (S), boron (B), and halogen (F, Cl, Br, I) and also carbon (C) and nitrogen (N) (for self-doping), as they are easily accessible and can be introduced into the g-C₃N₄ framework through different physical and chemical synthetic methods. In this review article, the structural and optical properties of g-C₃N₄ is introduced first, followed by a brief introduction to the modification of g-C₃N₄ as photocatalysts. Then, the progress in the non-metal doped g-C₃N₄ with improved photocatalytic activity is reviewed in detail, with the photocatalytic mechanisms presented for easy understanding of the fundamentals of photocatalysis and for guiding in the design of novel g-C₃N₄ photocatalysts. Finally, the prospects of the modification of g-C₃N₄ for further advances in photocatalysis is presented.     

石墨相氮化碳/二氧化锡复合材料的制备及光催化性能

采用热聚合法和水热法相结合的方法制备了g-C_3N_4/SnO_2复合光催化剂。利用XRD、SEM、TEM、FT-IR和UV-Vis DRS等多种测试手段对所得样品的物相结构、微观形貌和吸光特性等进行了表征。结果表明,异质结构复合光催化剂的最大光吸收边位置相对纯相SnO_2发生了明显的红移,并且SnO_2颗粒均匀分布于g-C_3N_4表面,其中最优组分(50%-g-C_3N_4/SnO_2)光催化降解染料罗丹明B(RhB)的效率达到了纯相g-C_3N_4的3.78倍。     

不同取代基巯基偶氮苯甲酸TiO2光催化降解的密度泛函理论研究

以TiO2为光催化剂,对含六种不同取代基的巯基偶氮苯甲酸进行了光催化降解实验,并采用量子化学密度泛函理论B3LYP/6-31G**计算了巯基偶氮苯甲酸的电子结构,研究了巯基偶氮苯甲酸中推、拉电子取代基对其光催化降解活性的影响.结果表明,拉电子基(-COOH或-SO3H)的引入使巯基偶氮苯甲酸的偶极矩增大,绝对电负性减小,最高占有轨道能量升高,HOMO-LUMO能隙和C-N键的键级降低,从而提高了巯基偶氮苯甲酸的光催化降解活性,而分子中推电子基团的影响则相反.     

微波增强H3PW12O40／TiO2光催化降解染料和水杨酸的研究

以孔雀石绿为模型分子, 考察了微波无极灯的形状、微波功率和溶液初始浓度对光催化降解效果的影响. 并且在最佳微波反应条件下, 考察了通过溶胶-凝胶再结合程序升温水热法制备的复合材料H3PW12O40/TiO2对刚果红、酸性黑、酸性品红和水杨酸的光催化降解情况. 结果表明, 微波无极灯具有更好地增强H3PW12O40/TiO2光催化降解有机污染物的作用.     

石墨烯量子点修饰的BiOI/PAN柔性纤维的制备及其增强的光催化活性

In environment remediation, photocatalytic oxidation is a promising technique for removing organic pollutants. Compared to adsorption, biodegradation, and chemical oxidation, photocatalytic oxidation can eliminate organic pollutants completely, conveniently, and cheaply in an environmentally friendly manner. Visible-light-driven photocatalytic oxidation is particularly advisable because of the high proportion of visible light energy in solar energy. Bismuth oxyiodide (BiOI) is a promising visible-light-driven photocatalyst for the oxidization of pollutants, not only because of its narrow band gap, but also for its relatively low valence band (VB), which is adequate for photogenerated holes to oxidize a variety of organic compounds. However, the shortcomings of BiOI powder, such the difficulty of recycling it, its low surface area, and fast carrier recombination, limit its practical applications. Meanwhile, the flexibility and hierarchical structure of photocatalysts are particularly advisable because these properties are beneficial for the convenient operation, recycling, and performance improvement of these materials. Herein, based on an electro-spun polyacrylonitrile (PAN) nanofiber substrate, a hierarchical BiOI/PAN fiber was prepared through an in situ reaction. In the as-prepared BiOI/PAN fibers, BiOI flakes were aligned vertically and uniformly around the PAN fibers. BiOI nuclei generated from pre-introduced Bi(Ⅲ) in the PAN fiber act as seeds for the growth of BiOI nanoplates, which is crucial for the formation of a hierarchical structure. Such a hierarchical structure can improve both the light absorption and carrier generation of the BiOI/PAN fibers, as demonstrated by UV-Vis diffuse reflectance spectra and photoluminescence emission. Therefore, the BiOI/PAN fibers exhibited higher photocatalytic activity than BiOI powder. When the BiOI/PAN fibers were decorated with pre-prepared graphene quantum dots (GQDs), a GQD-modified BiOI/PAN fibrous composite (GQD-BiOI/PAN) was fabricated. The morphology of the obtained GQD-BiOI/PAN fibers was nearly the same as that of the BiOI/PAN fibers. A step-scheme (S-scheme) heterojunction was formed between the GQDs and BiOI, which was confirmed by the fabrication method, photoluminescence emission, reactive radical tests, and XPS analysis. This kind of S-scheme heterojunction can not only effectively suppress the recombination of photogenerated holes, but can also reserve the more reductive electrons on the lowest unoccupied molecular orbital of GQDs and the more oxidative holes on the VB of BiOI, for the photocatalytic degradation of phenol. Because of the fibrous hierarchical structure and S-scheme heterojunction, GQD-BiOI/PAN outperformed BiOI nanoparticles and BiOI/PAN nanofibers in the photocatalytic oxidation of phenol under visible light. In addition, because of tight bonding, GQD-BiOI/PAN can be tailored and operated by hand, which is convenient for recycling. During recycling, no obvious loss of sample or decrease in photocatalytic activity was observed. This work provides a new pathway for the fabrication of flexible photocatalysts and a new insight into the enhancement of photocatalysts.