微波修饰g-C3N4处理罗丹明B模拟废水的研究

以三聚氰胺(C_3H_6N_6)为前驱体,通过高温煅烧制备了g-C_3N_4光催化剂,并用微波辐射法制备了改性g-C_3N_4,用XRD、FT-IR、UV-Vis及PL等对催化剂结构进行了表征。结果表明,微波改性样品光催化活性显著提高,微波辐射7min的催化剂对20mg/L的罗丹明B在可见光下催化降解2h,降解率达到97.03%。     

g-C3N4/ZnCo2O4微球的制备及光催化降解四环素

以ZnCo2O4微球材料为基础材料,采用溶液分散吸附和100 oC下恒温12 h方法制备了g-C3N4负载的ZnCo2O4复合材料,并采用X-射线衍射(XRD)、扫描电镜(SEM)、光电子能谱(XPS)和固体紫外漫反射(Uv-DRS)技术对其进行了表征。ZnCo2O4与g-C3N4之间形成异质结结构,禁带宽度值为1.73 eV。在可见光的照射下,ZnCo2O4的光生电子(e‒)在异质结处的C3N4的离域π键所捕获,有效的促进了ZnCo2O4的光生电子(e‒)和光生空穴(h+)分离,ZnCo2O4的光生空穴(h+)是光催化降解四环素水溶液的主要因素。在可见光下,初始浓度为10 mg/L的四环素水溶液(C22H24N2O8)最高降解率可达到90.02 %。     

Intensifying the photocatalytic degradation of methylene blue by the formation of BiFeO3/Fe3O4 nanointerfaces

A novel highly efficient photocatalyst composite BiFeO₃/Fe₃O₄ has been synthesized by mechanosynthesis and applied to the degradation of Methylene Blue under visible light. Structural, optical and photocatalytic properties of the proposed photocatalyst composites are carefully investigated. The nanointerfaces, associated to ferrous Fe²⁺ ions of the Fe₃O₄ nanoparticles, improve the photocatalytic efficiency when compared with pure BiFeO₃ or Fe₃O₄. The time required to the complete degradation of Methylene Blue solution is 40 min for the sample with 20% of Fe₃O₄ which is more than 7 times faster than the time required using BiFeO₃ alone. Moreover, with the addition of H₂O₂ a complete degradation is achieved just after 10 min, which is faster than any other photocatalytic reaction reported for BiFeO₃-based materials. This enhancement is assumed to be related to an electron drain process due to the difference between energy levels of the conduction bands of BiFeO₃ and Fe₃O₄ combined with the direct Fenton-like process associated with the Fe²⁺ ions of the composites.     

MoO3/g-C3N4复合材料的制备及光催化性能

以三聚氰胺和四水合钼酸铵为前驱体,采用水热法制备了MoO₃/g-C₃N₄复合光催化剂。利用X-射线衍射仪（XRD）、红外光谱仪（FT-IR）、扫描电子显微镜（SEM）、X射线光电子能谱仪（XPS）及紫外-可见漫反射仪（DRS）等对制备的样品进行了表征。表征结果显示,棒状的三氧化钼负载在层状C₃N₄表面,复合材料的光吸收能力有一定的增强。材料可见光催化降解亚甲基蓝（MB）溶液的实验表明,三氧化钼和g-C₃N₄所复合产生的异质结具有较好的吸收光强度及催化降解性能,尤其是5%（质量分数）MoO₃/g-C₃N₄复合材料光催化降解率最好,达到95.7%,高于纯三氧化钼和g-C₃N₄。自由基与空穴捕获实验表明,·O₂^-是光催化反应中的主要活性物种。MoO₃/g-C₃N₄复合材料在4个循环周期内表现出了优异的稳定性。     

Tungsten-doped foam g-C3N4 with improved photocatalytic properties for degradation of pollutant and hydrogen evolution

As a potential material applied in the photocatalytic field, graphitic carbon nitride (g-C₃N₄) has attracted extensive attention for its advantages of visible-light response, excellent thermodynamic, and chemical stability. However, the photocatalytic performance of g-C₃N₄ is still limited in practical applications. Here, using a facile thermal polymerization method, unique W-doped foam g-C₃N₄ was synthesized to realize enhanced photocatalytic performance for the degradation of Rhodamine B and the evolution of hydrogen. Compared with pure foam g-C₃N₄, tungsten doping modified the foam g-C₃N₄ and efficiently improved its specific surface area, leading to enhanced photocatalytic performance. The average rate of hydrogen evolution was as high as 8818 μmol·h⁻¹·g⁻¹, which was better than most photocatalysts. This work proposes a new effective method and idea to modify g-C₃N₄ for improving its photocatalytic performance.     

固相反应合成ZnO/g-C3N4光催化剂及光催化性能

以乙酸锌、氢氧化钠和g-C₃N₄粉末为原料,并添加十二烷基苯磺酸钠粉末作为表面活性剂,采用室温固相研磨法制备了ZnO/g-C₃N₄光催化剂。并研究了复合材料的光催化性能。研究结果表明,经固相研磨后,会形成ZnO/g-C₃N₄复合材料,g-C₃N₄充分细化成薄片状。添加十二烷基苯磺酸钠粉末促进了g-C₃N₄发生相变。当g-C₃N₄含量较低时,产物的形貌呈现为纳米花,实际上是因为大量的氧化锌纳米片负载到g-C₃N₄片上。当g-C₃N₄含量较高时,产物为二维纳米片,由氧化锌纳米颗粒负载到g-C₃N₄片上。合成的ZnO/g-C₃N₄复合材料对亚甲基蓝表现出良好的可见光催化活性。     

TiO_2光催化降解有机污染物的研究进展

二氧化钛具有优异的光电转换及物化性能,是半导体光催化材料的研究热点,广泛用于有机污染物降解研究。但二氧化钛禁带宽度较大,只能吸收紫外光辐射,太阳光利用率低,且二氧化钛的量子效率低。综述金属掺杂、非金属掺杂、共掺杂、半导体复合-异质结和染料敏化二氧化钛改性方法,拓宽TiO_2的光响应范围,抑制载流子复合,提高光催化活性和能量转换效率,提高有机污染物降解率,实现可见光降解。     

Enhanced performance of g-C3N4/TiO2 photocatalysts for degradation of organic pollutants under visible light☆

Photocatalytic degradation is one of the most promising remediation technologies in terms of advanced oxida-tion processes (AOPs) for water treatment. In this study, novel graphitic carbon nitride/titanium dioxide (g-C3N4/TiO2) composites were synthesized by a facile sonication method. The physicochemical properties of the photocatalyst with different mass ratios of g-C3N4 to TiO2 were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), N2 sorption, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and UV–vis DRS. The photocatalytic performances were evaluated by degradation of methylene blue. It was found that g-C3N4/TiO2 with a mass ratio of 1.5:1 exhib-ited the best degradation performance. Under UV, the degradation rate of g-C3N4/TiO2 was 6.92 and 2.65 times higher than g-C3N4 and TiO2, respectively. While under visible light, the enhancement factors became 9.27 (to g-C3N4) and 7.03 (to TiO2). The improved photocatalytic activity was ascribed to the interfacial charge transfer between g-C3N4 and TiO2. This work suggests that hybridization can produce promising solar materials for envi-ronmental remediation.     

Co3O4/g-C3N4复合光催化剂降解罗丹明B的研究

为提高石墨相氮化碳(g-C3N4)的光催化性能,采用3D花状ZIF-Co与g-C3N4混合热处理的方法制备了3D花状Co3O4/g-C3N4复合光催化剂,并将其用于光催化降解罗丹明B模拟染料废水。结果表明:当ZIF-Co与g-C3N4的质量比为5%时,制备的Co3O4/g-C3N4的光催化性能最佳,在可见光下照射30 min,其对罗丹明B的降解率可达90%以上,且该催化剂的重复稳定性好。在降解罗丹明B的过程中活性基团的作用顺序为·O2->h+>·OH。     

Investigation of g-C3N4/ZnAl2O4 and ZnO/ZnAl2O4 nanocomposites: From synthesis to photocatalytic activity of pollutant dye model

The fabrication of nanocomposite photocatalytsts with excellent photocatalytic activity is an important step in the improved degradation of organic dyes. A series of nanocomposite photocatalysts was synthesized with g-C₃N₄ and ZnO loading contents of 10, 20 and 30%. The nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). The optical band gaps of g-C₃N₄, ZnO and ZnAl₂O₄ were about 2.79, 3.21 and 3.55 eV, respectively. Methylene blue (MB) was degraded over the prepared photocatalysts under UV irradiation. Photocatalytic activity was about 9.1 and 9.6 times higher, respectively, on 20%g-C₃N₄/ZnAl₂O₄ and 20%ZnO/ZnAl₂O₄ nanocomposite photocatalysts than on pure ZnAl₂O₄ spinel powders. Recycling experiments showed that 20%g-C₃N₄/ZnAl₂O₄ and 20%ZnO/ZnAl₂O₄ nanocomposite photocatalysts exhibited good stability after five cycles of use.     

CDs/ZnO/g-C3N4三元组份协同作用促进光催化降解染料

采用浸渍-热聚合法制备CDs/ZnO/g-C3N4复合材料，考察其对罗丹明B的光降解效率。利用 XRD、TEM、XPS、UV-Vis DRS、FI-IR等手段对催化剂进行表征和评价。结果表明：CDs/ZnO/g-C3N4仍保持石墨相g-C3N4的晶型结构，三元组份相互协同作用使CDs/ZnO/g-C3N4表现出优异的光催化性能，其降解罗丹明B的效果优于单体g-C3N4、ZnO及ZnO/g-C3N4，脱色率可达到70%左右。     

Enhanced visible-light photocatalytic properties of g-C3N4 by coupling with ZnAl2O4

A series of g-C₃N₄/ZnAl₂O₄ composites were prepared using a conventional calcination method and the heterostructures were systematically characterized. It was found that the combination of g-C₃N₄ with ZnAl₂O₄ significantly improve their photocatalytic activities. The optimum photocatalyst of composite is at 5% (wt%) of ZnAl₂O₄, whose degradation efficiency for methyl orange (MO) was 96% within 120 min under visible-light irradiation. The formation of heterojunction between g-C₃N₄ and ZnAl₂O₄ can facilitate efficient charge separation of photogenerated electron-hole pairs, which were confirmed by electrochemical impedance spectroscopy (EIS). As a result, the photocatalytic properties of composites were enhanced.     

Controlled synthesis of Ag2O/g-C3N4 heterostructures using soft and hard templates for efficient and enhanced visible-light degradation of ciprofloxacin

Pluronic 31R1 surfactant and MCM-41 silica were used to fabricate mesoporous Ag₂O/g-C₃N₄ heterostructures with improved surface areas. The fabricated mesoporous nanocomposite was used to photo oxidize ciprofloxacin. The TEM images of Ag₂O/g-C₃N₄ indicated a uniform dispersion of spherical approximately 4-nm Ag₂O nanoparticles on g-C₃N₄. The mesoporous 0.9% Ag₂O@g-C₃N₄ heterostructure exhibited 100% efficiency in ciprofloxacin oxidation within 60 min when compared with the 25% efficiency in 120 min of pure mesoporous Ag₂O and 10% efficiency in 120 min of pure g-C₃N₄. The highest ciprofloxacin oxidation efficiency achieved was 100%, which was four and ten times better than those of Ag₂O and g-C₃N₄, respectively. This superior performance of the mesoporous Ag₂O/g-C₃N₄ was attributed to the high dispersion of nano-sized mesoporous Ag₂O particles on the g-C₃N₄ surface, narrow bandgap, and significantly high surface areas. The powerful interaction between Ag₂O and g-C₃N₄ ensured robust durability of Ag₂O/g-C₃N₄ heterostructures, which is evident in the fact that five recycling trials of the photocatalyst rendered a minimal loss of efficiency.     

Effects of solvent-induced morphology evolution of Zn2GeO4 on photocatalytic activities of g-C3N4/Zn2GeO4 composites

Morphology modulation of photocatalyst has been demonstrated to be a crucial strategy for improving the catalytic performance in solar energy conversion system. Here we systematically investigated the influence of the solvent-dependent morphology evolution of Zn₂GeO₄ phase on the photocatalytic efficiency of the as-prepared g-C₃N₄/Zn₂GeO₄ composites. The morphologies of Zn₂GeO₄ were rationally tuned from flower-like nanosheets to length-controllable nanorods, and microclusters assembled from microrods through regulating the solution polarity of different organic solvents. Accordingly, the Zn₂GeO₄ sample prepared in ethylene glycol (EG) with long rod-like morphology and integrated with g-C₃N₄, abbreviated as g-C₃N₄/Zn₂GeO₄(1:1)-EG, exhibited the best visible-light absorption ability and the highest efficiency. The synergetic effect of the long rod-like Zn₂GeO₄ phase with many exposed (110) crystalline facets and g-C₃N₄ accelerates the separation and interface transportation of photoexcited charge carriers, as confirmed by photocurrent measurements. The MB degradation mechanism was also proposed to clarify the charge-transfer process and the improved photodegradation activity. This study offers an experimental basis for understanding the significance of morphology control on rational design of photocatalysts with improved performance.     

g-C3N4/ZnO复合材料的制备、表征及可见光催化性能

以一步法原位合成了g-C3N4/ZnO异质结复合材料,评价其在可见光下降解亚甲基蓝（MB）的光催化活性,并探讨了g-C3N4/ZnO的光催化机制。运用XRD、FT-IR、SEM和UV-Vis DRS对所合成的复合材料进行表征。结果表明,经复合后g-C3N4和ZnO紧密结合,构建了异质结,提高了光生电子-空穴的分离效率,并且在可见光区表现出较强的光响应性;当g-C3N4的质量分数为19%时,复合材料降解MB的反应速率常数为0.0206min-1,是纯g-C3N4的3.8倍。催化剂重复使用5次,仍保持较高的催化活性。     

花簇状g-C3N4/Bi2MoO6微球的制备及光催化降解模拟染料废水

以酵母为生物模板，通过水热-牺牲模板法制备得到了花簇状g-C3N4/Bi2MoO6复合微球，利用XRD、SEM、TEM、FT-IR、DRS、光电流响应以及氮气吸附-脱附等手段对样品的晶体结构、微观形貌、光吸收和比表面积等性能进行表征，并对样品可见光催化降解亚甲基蓝（MB）模拟染料废水的性能和机理进行探讨。实验结果表明：水热-牺牲模板法可实现g-C3N4与Bi2MoO6在生物模板表面的成功复合，样品分散性良好，微球直径约为8μm，表面呈花簇状，比表面积达11.6007m2/g。在可见光下复合微球对亚甲基蓝模拟染料废水表现出较高的光催化降解活性，当催化剂添加量为1g/L，可见光照射120min后，初始浓度为15mg/L的亚甲基蓝废水降解率高达96%以上。机理分析证实花簇状复合微米球表面g-C3N4与Bi2MoO6形成的Z型异质结有效降低了电子-空穴的复合率，显著提升了对模拟染料废水的可见光催化性能。     

Selective photocatalytic degradation of organic pollutants by CuxS/ZnO/TiO2 heterostructures

Photoactive heterostructures containing Cu_xS/ZnO/TiO₂ have been obtained by spray pyrolysis deposition followed by post-deposition thermal treatment. The ZnO middle layer morphology was tailored by using chemical additives during the deposition. The samples have crystalline structure with average crystallite size around 80 Å for metal oxides and 90 Å for Cu_xS. The roughness varies from 27.5 nm for Cu_xS/dZnO/TiO₂ to 33.6 nm for Cu_xS/pZnO/TiO₂ samples. The wettability properties were tested based on the contact angle measurements. The highest surface energy value (106.4 mN/m) corresponding to Cu_xS/pZnO/TiO₂ with 30 min UV irradiation, with a predominant polar component of 85.3 mN/m. The photocatalytic efficiency under UV–Vis light irradiation was evaluated using methylene blue and phenol as pollutants. The highest photocatalytic values (93.4% for methylene blue and 72.3% for phenol) were obtained for Cu_xS/pZnO/TiO₂ heterostructure with successive 30 min UV irradiation at 2 h intervals. The mineralization efficiency was tested using total organic carbon analysis and the results are slightly lower compared with photocatalytic efficiency.     

Fabrication and photocatalytic properties of novel ZnO/ZnAl2O4 nanocomposite with ZnAl2O4 dispersed inside ZnO network

Novel ZnO/ZnAl₂O₄ nanocomposites with ZnAl₂O₄ nanoparticles homogeneously dispersed inside a network of ZnO are fabricated by thermal treatment of a single‐source precursor of ZnAl‐layered double hydroxides (ZnAl‐LDHs) at 800°C. The effects of the Zn/Al molar ratio of the LDH precursors on the structure, composition, morphology, textural as well as UV‐absorbing properties and photocatalytic activities of the nanocomposites are investigated in detail. The results show that the ZnO/ZnAl₂O₄ nanocomposites derived from the ZnAl‐LDHs precursors have superior photocatalytic performances to either single phase ZnO or similar ZnO/ZnAl₂O₄ samples fabricated by chemical coprecipitation or physical mixing method. The heterojunction nanostructure and the strong coupling between the ZnO and ZnAl₂O₄ phase derived from ZnAl‐LDHs precursors are proposed to contribute the efficient spatial separation between the photo‐generated electrons and holes, which can concomitantly improve the photocatalytic activities. © 2011 American Institute of Chemical Engineers AIChE J, 2012