提高石墨相氮化碳光催化效率的研究进展

石墨相氮化碳(g-C3N4)是一种不含金属元素,且能利用可见光的半导体光催化剂,在光催化领域具有应用潜力。但量子效率低是g-C3N4在光催化领域面临的主要问题。因此研究人员提出很多策略来设法提高g-C3N4的光催化效率,本文对目前出现的几种提高光催化效率的热门方法做出简要综述,为今后进一步以提高g-C3N4的光催化效率提供理论基础。     

铁改性石墨相氮化碳催化苯酚羟基化反应合成二酚

石墨相氮化碳(g-C3N4)以其独特的电子结构和化学特性引起了广泛关注。以双氰胺和硝酸铁为原料,制备了Fe改性的石墨相氮化碳(Fe/ g-C3N4),采用红外光谱、XRD和N2吸附-脱附等分析手段对g-C3N4和 Fe/g-C3N4 进行了表征,并用以催化苯酚羟基化反应合成二酚,研究了Fe/ g-C3N4催化性能的影响因素。结果表明,Fe/ g-C3N4材料具有良好的介孔结构,Fe的引入改变了g-C3N4层状结构的层间距。当苯酚/H2O2摩尔比为2/1、铁负载量为0.7%(质量分数)、反应温度为50 ℃、反应时间为6 h时,苯酚的转化率达到39.7%,邻苯二酚和对苯二酚的总选择性为85.8%。重复实验结果证实该催化剂可以重复使用。     

Ni-MoO_3/La~(3+)-TiO_2/ZrAlO光催化CO_2和CH_3OH直接合成DMC

制备了CO_2和甲醇直接合成碳酸二甲酯的光催化剂Ni-MoO_3/LT-ZAO(复合载体La~(3+)-TiO_2/ZrAlO),以XRD、H_2-TPR、N_2吸附脱附表征了催化剂及载体的物相组成及还原性能,测定了催化剂及载体的比表面积和比孔容,采用紫外-可见漫反射光谱(UV-Vis DRS)表征了光催化剂的光吸收性能,用连续流动固定床反应器评价了催化剂的光催化性能。结果表明:在TiO_2中掺杂La_2O_3使得催化剂的光吸收边带向可见光区迁移;MoO_3和La_2O_3使催化剂对可见光的吸收强度增强,有利于提高催化剂的光催化性能。12%(Ni-MoO_3)/LT-ZAO光催化剂显示出最好的活性和较好的选择性,其甲醇转化率高达12.1%而对DMC的选择性为91.1%。     

ZnO/mpg-C3N4复合光催化剂的制备及其可见光催化性能

采用简单溶剂热法成功合成了具有高可见光催化活性的ZnO/mpg-C₃N₄复合光催化剂。利用XRD、TEM、FT-IR、UV-Vis等手段对样品的结构、形貌及光学性能进行了表征,并以亚甲基蓝(MB)作为目标污染物,对ZnO/mpg-C₃N₄进行了光催化降解评价实验。结果表明,采用溶剂热法合成的ZnO/mpg-C₃N₄复合光催化剂中,ZnO颗粒较均匀地分散在mpg-C₃N₄上,与纯ZnO及mpg-C₃N₄相比,可见光催化活性明显提高。当mpg-C₃N₄质量分数为80%时,ZnO/mpg-C₃N₄复合光催化剂的光催化活性最高,为纯mpg-C₃N₄的2.3倍。     

CdS/CeO2异质结纳米光催化剂催化还原CO2的研究

采用水热法制备CdS/CeO₂异质结纳米光催化剂，并采用X射线粉末衍射、高分辨率透射电子显微镜、紫外-可见光谱等对所合成催化剂的物理化学性质进行表征，评价其光催化CO₂还原性能。结果表明：相比于CdS及CeO₂纳米颗粒，CdS/CeO₂异质结纳米光催化剂可拓宽催化剂的可见光吸收范围，降低带隙，有效延缓电子-空穴对的复合，降低电弧半径及电子-空穴对转移运动电阻，从而提高催化剂的可见光感应范围及光催化活性，证实半导体复合制备的异质结纳米结构可有效提高催化剂光催化还原CO₂的活性；1 mmol Cd(OOCCH₃)₂·2H₂O水溶液中加入100 mg CeO₂纳米颗粒所制备的异质结纳米光催化剂CdCe-100具有最优的光催化CO₂还原性能，在反应时间为10 h时，CO产率为213μmol/g, CH₃OH产率为1 534μmol/g,且重复利用6次时催化...     

Au/Cu2O@Au可见光催化CO2还原性能

为提高光催化还原二氧化碳(CO₂)的产物产率和选择性，采用一步法在空腔氧化亚铜(Cu₂O)中引入金属Au,制备了Au/Cu₂O@Au光催化剂。通过XRD、SEM、TEM、XPS、紫外-可见吸收光谱等表征和光电化学性能测试对光催化剂进行分析，考察了Au/Cu₂O@Au光催化剂催化还原CO₂性能。结果表明：Au/Cu₂O@Au光催化剂具有优异的性能，在光照强度为20 mW/cm²的可见光照射下，该光催化剂将CO₂光催化还原为甲烷(CH₄)和一氧化碳(CO)的产率分别为4.86和42.04μmol/(g·h),选择性分别为31.62%和68.38%。与空腔Cu₂O光催化剂相比，CO产率提高了8.12倍，选择性提高了32.84百分点。一步法合成的Au/Cu₂O@Au光催化剂中的Au颗粒分布在Cu₂O的表面和空腔内部，独特的Au分布与空...     

WO3/ZnO的制备及其光催化降解染料废水研究

采用直接沉淀法合成了一系列不同WO_3负载量的WO_3/ZnO复合光催化剂,并利用X射线衍射(XRD)对产物的晶体结构进行了表征。通过光催化降解染料废水对WO_3/ZnO的光催化性能进行评价。结果表明,负载WO_3后的ZnO比纯ZnO的结晶度高,且光催化性能也显著提高。在20 mg/L的罗丹明B溶液中加入0.6 g/L的10%WO_3/ZnO光催化剂,降解率可达93.3%。WO_3/ZnO光催化稳定性良好,重复使用4次后对罗丹明B的降解率仍在90.0%以上。     

微波法制备银镁共掺氧化锌复合光催化剂及其光催化性能研究

采用环形聚焦单模微波辅助法（简称微波法）快速合成银镁共掺氧化锌复合光催化剂（简称复合光催化剂）,并运用X射线衍射、扫描电子显微镜对其结构和形貌进行表征。将此复合光催化剂应用于光催化降解罗丹明B和含油污水,研究其光催化性能并探究光催化降解机理。结果表明：微波法合成的复合光催化剂具有良好的光催化性能,对含油污水的降解率优于商用二氧化钛;复合光催化剂重复使用4次后罗丹明B的降解率仍维持在92%以上,化学稳定性良好。。     

二苯基蒽唑啉类化合物光催化降解亚甲基蓝

以Friedl?nder缩合反应等步骤合成得到二苯基蒽唑啉类化合物,考察了8种二苯基蒽唑啉类化合物作为光催化剂降解亚甲基蓝溶液的性能。实验结果表明:8种二苯基蒽唑啉类化合物对亚甲基蓝溶液均有良好的光催化活性,进行光催化反应12 h后,催化剂对亚甲基蓝溶液COD_(Cr)去除率达54.1%～96.3%。其中2,8-二(4′-二苯氨基)苯基-4,6-二苯基-1,9-蒽唑啉和2,6-二(3′-N-乙基咔唑基)-4,8-二苯基-1,5-蒽唑啉表现出较高的光催化降解效果, 12 h COD_(Cr)去除率分别为96.3%和95.8%,光催化剂可以连续使用4次,在10 h内对两种模拟染料溶液的脱色率均可达到99%以上,COD_(Cr)去除率均可达到91%以上。     

钯锡改性纳米二氧化钛光催化还原二氧化碳的研究

采用光化学还原法,在复合半导体基础上表面作进一步钯改性,制备了钯锡改性的纳米二氧化钛光催化剂Pd-SnO2/TiO2,以二氧化碳光催化还原反应为探针,对催化剂进行了评价,并与复合半导体基础上,表面铜改性光催化剂的光催化还原性能进行了比较。结果表明,表面钯改性、二氧化碳光催化还原产物只检测到甲醇,这说明,复合半导体基础上钯的沉积,比铜掺杂更有利于深度还原产物甲醇的生成。结合XRD、XPS、TEM等催化剂表征结果,对钯锡改性纳米二氧化钛光激发机制进行了讨论,提出了二氧化碳光催化还原的可能机制。     

高效三相光催化剂BiVO4@C3N4@GO的制备及性能研究

NBiVO4, BiVO4@C3N4 and BiVO4@C3N4@GO composite photocatalysts were synthesized, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer(EDS), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), Fourier Transform Infrared Spectroscopy(FT-IR), and Brunauer-Emmett-Teller (BET) surface area techniques. The photocatalytic activity was evaluated for the degradation of the methylene blue (MB) under visible light irradiation and BiVO4@C3N4@GO ternary composite outperformed the binary composites, BiVO4@C3N4 and BiVO4. Then the effects of catalyst dosage, initial pH, and initial methylene blue concentration on degradation process were investigated systematically. The improvement of visible-light photocatalytic degradation performance was attributed to the enhanced visible light absorption, larger surface area, higher adsorption ability, and prolonged lifetime of photo-generated electron-hole pairs. The recycle experiments results showed that the BiVO4@C3N4@GO composite have excellent photo-stability for MB photocatalytic degradation.     

Fe2O3复合BiOCl的制备及其光催化性能研究

Fe2O3 was synthesized by the solvothermal method, and the synthesized Fe2O3 was added in the process of preparing BiOCl by hydrolysis, and then Fe2O3/BiOCl photocatalytic materials with different composite ratios were prepared. The optimal Fe2O3/BiOCl (1Fe/50Bi) sample showed a highest photocatalytic efficiency for cationic dyes (Rhodamine B) and anionic dye (methyl orange) degradation irradiated with visible light, as compared with that of a bare BiOCl catalyst. Meanwhile, radical capturing experiments indicated that the photo-induced holes (h+) is the main active species. X-ray powder diffraction and ultraviolet-visible diffuse reflectance spectroscopy were used to characterize the structural and optical properties, which proved that Fe2O3 was successfully composited to the BiOCl surface and effectively reduced the bandgap of BiOCl. More importantly, the optimal 1Fe/50Bi sample shows the highest photocatalytic efficiency for tetracycline (TC) degradation (98%) irradiated with visible light, as compared with that of a bare BiOCl catalyst. Consequently, the Fe2O3/BiOCl photocatalyst have potential applications in environmental purification.     

新型键联异质结CoMOF-g-C3N4-COOH用于可见光光解水产氢反应

基于钴金属有机骨架(CoMOF)和羧基化g-C₃N₄-COOH,设计合成了依靠化学键连接形成异质结界面的新型光催化剂CoMOF-g-C₃N₄-COOH。CoMOF-g-C₃N₄-COOH异质结材料具有优异的可见光下光解水制氢性能,产氢速率达到233 μmol/(g·h),与传统静电吸附合成的CoMOF-g-C₃N₄或纯g-C₃N₄-COOH相比,性能大幅提升。这是由于CoMOF/g-C₃N₄异质界面处化学键的设计构建,促进了光生载流子的传递,能够有效抑制电荷-空穴的复合。该工作证明了复合催化剂异质界面处成键对光生电子高效转移的作用,为设计高效光解水产氢的MOF基材料提供了新的思路。     

硫掺杂g-C3N4多孔纳米片的制备及其光催化降解性能研究

Abstract: In this study, sulfur-doped porous g-C3N4 nanosheets (CN-T-U 1.75) have been synthesized successfully by one-step calcination using urea and thiourea as the precursors. CN-T-U 1.75 exhibited excellent photocatalytic performance for Rhodamine B (RhB) degradation under visible light irradiation, with the kinetic reaction rate constant of 0.01838 min-1. Analysis of the characterization results showed that CN-T-U 1.75 had a larger specific surface area, and the doping caused a change in the energy band structure. Moreover, the catalytic mechanism analysis shows it could produce two oxidation groups of ?O2- and ?OH to degrade pollutants synergistically.     

高分散的CoWO4或CuWO4提高WO3的光催化性能

本文采用原位浸渍与固相反应结合,成功地合成了CoWO4或CuWO4高度分散在WO3表面的复合CoWO4/WO3或CuWO4/WO3光催化剂。通过XRD,SEM,TEM,EDS,HR-TEM,UV-vis DRS,SPV和活性物种实验研究了CoWO4/WO3和CuWO4/WO3样品的结构,形貌,光物理性质和光催化降解机理。XRD,SEM和TEM结果表明,当CoWO4或CuWO4的负载量较小时,CoWO4或CuWO4高度分散在WO3表面上。但是当CoWO4或CuWO4的负载量增加时,WO3表面的CoWO4或CuWO4颗粒发生明显的团聚。可见光光催化降解RhB的实验结果表明,所有CoWO4/WO3或CuWO4/WO3样品的光催化活性都优于WO3的活性。这主要是因为WO3和CoWO4或CuWO4之间形成的II型异质结能够显著促进光生电子和空穴的分离。此外,CoWO4/WO3和CuWO4/WO3系列样品中,0.2％CoWO4/WO3和0.2％CuWO4/WO3分别显示了最优异的光催化活性,与WO3相比,其光催化活性分别提高了约9.1倍和6.8倍。此外,活性物种实验表明,光催化过程中在0.2％CoWO4/WO3和0.2％CuWO4/WO3催化剂上产生的?OH,h+和?O2?都是光催化降解RhB的活性物种。本文为设计高活性的光催化剂提供了一种思路。     

Preparation characterization and non-isothermal decomposition kinetics of different carbon nitride sheets

Three series of graphitic carbon nitride g-C3N4 namely bulk (BCN), sulfur-doped (SCN) and thin layer (TCN) sheets are prepared using urea precursor under a microwave thermal pyrolysis. Several analytical techniques are used to characterize the obtained g-C3N4 products namely, XRD, FTIR, TEM, SPR, DRS, and BET. To study the thermal stability of the synthesized graphite-like materials, the solid-state decomposition kinetics of BCN, SCN and TCH products were investigated using TGA. The energy of activation E_a and the frequency factor A. Decomposition pathway were investigated using four mathematical methods and 35 mechanisms (g(α)) models. The computed thermodynamic parameters proved that the thermal deformation mechanism of g-C3N4 sheets depends on the diffusion process. The SCN and TCN sheets are less order in the deformation arrangement and possess higher entropy (ΔS°). The arrangement in the 2nd deformation stage of TCN is higher than in the dehydration stage.