氮化碳材料的光谱学分析及光催化性能研究

为克服光催化材料可见光利用效率低的缺陷, 通过三聚氰胺高温缩聚的方法合成了石墨型氮化碳(g-C3N4)材料。采用XRD, SEM, UV-Vis技术对氮化碳材料的微观结构和光学性能进行了表征, 并通过降解罗丹明B溶液研究了缩聚温度和不同光源对光催化效率的影响。结果表明, 合成的氮化碳层片状结构保存良好, 尽管材料表面在高温下断裂形成了不规则的块体颗粒;随着煅烧温度的升高, 催化剂在紫外光和可见光部分的吸收都显著增强, 这可能是由于材料表面的岩石状块体颗粒提高了材料的比表面积, 同时降低了光的反射又提高了对光的吸收。在罗丹明B的光降解测试中, 催化剂在可见光和太阳光照射下均表现出了良好的催化效果, 缩聚温度为580 ℃时效果最好, 分别为94.8%(60 min)和91.1%(90 min)。该方法制备的石墨型氮化碳催化剂对利用清洁能源进行环境净化应用具有极大的潜在价值。     

硝酸辅助合成氮缺陷石墨型氮化碳材料及光谱学分析

通过硝酸辅助高温缩聚三聚氰胺的方法合成了氮缺陷石墨型氮化碳(g-C_3N_4)光催化材料,并利用scanning electron microscope (SEM), brunauer emmett teller (BET), X射线衍射(X-ray diffraction, XRD), ultraviolet-visible spectroscopy (UV-Vis), X射线光电子能谱(X-ray photoelectron spectroscopy, XPS)和Fourier transform infrared spectroscopy (FTIR)等手段对其微观结构和光谱学特征进行了分析, SEM给出了氮化碳和改性材料的表面微观形貌,改性材料表现出了更小的孔径与更加粗糙类似于"矾花"状的表面,说明硝酸的加入显著改变了材料的表面结构。BET图谱可以明显看出硝酸辅助合成材料显示出了较大的比表面积和孔径。XRD图谱显示改性后的材料保持了氮化碳材料的一般结构特征,并且两个特征峰均发生了峰宽以及角度的变化,说明了酸辅助可以改变原材料的结构。从UV-Vis图谱中看出改性材料发生了明显的红移现象,说明材料对可见光的响应较原始氮化碳材料有一定增强。FTIR图谱显示改性后材料在保持原有材料基团的基础上碳氮单键以及氨基基团增多等变化。从XPS图谱中发现改性材料的结合能以及峰面积发生变化,由此得出N元素含量显著提高,推测由于三聚氰胺与硝酸产生部分反应后被高温焙烧引入硝酸中的氮元素。最后测试了材料在可见光和太阳光照射下的催化性能。结果表明,该方法不仅简单易行,硝酸消耗量低,而且合成的g-C_3N_4材料具有很好的多孔结构、更小的粒度和更高的比表面积等微观结构优势,以及增强的光吸收响应特征,更重要的是与由其他方法合成材料的碳氮(C/N)比上升不同,该方法合成的材料C/N比有明显的下降趋势,氨基基团也有增多的表现,这可能因硝酸与三聚氰胺在高温烧结过程中的化学反应所导致。可见光和太阳光照射催化降解罗丹明B(RhB)的试验结果表明,当硝酸用量为2 mL时g-C_3N_4材料的催化效果最佳,降解率均达到99%,分别是无硝酸条件下的2.8倍和2.5倍,并且材料的循环性降解测试表明材料的可回收性强。这种高效易得、方便工业化推广和可回收性强的g-C_3N_4材料为今后的实际应用提供了极好的参考。     

Ag负载WO3/TiO2光催化剂的合成及其催化性能

以钛酸丁酯、无水乙醇、钨酸铵为原料,采用溶胶-凝胶法合成了WO3/TiO2复合光催化剂;采用光还原技术制备了Ag负载WO3/TiO2光催化剂,借助X射线粉末衍射(XRD)和UV-Vis光谱等技术对样品的组成和光吸收性能进行了表征,并以罗丹明B为模型污染物考察样品的光催化活性。XRD分析表明,所得粉体均为锐钛矿型纳米TiO2,且与WO3复合后,纳米TiO2特征衍射峰宽化,强度降低;UV-Vis光谱分析表明,载银使得催化剂在400—700nm的可见光区域对光响应,且在紫外光区吸收显著增强,对光具有更高的利用率;以罗丹明B为降解物的光催化实验表明,WO3复合对纳米TiO2光催化活性有显著的影响,而载Ag后其光催化活性进一步提高,将该光催化剂用于炼油厂废水的处理,效果较好。     

共聚改性g-C3N4-N可见光催化降解RhB的研究

染料废水的排放对人类健康和生态系统构成严重威胁,光催化技术因其操作简单、绿色环保等优点在解决环境污染问题上已显示出巨大的潜力。类石墨相氮化碳（g-C₃N₄）由于成本低且具有良好的化学稳定性,被认为是光催化领域最有前景的新型光催化剂之一,但由于单一g-C₃N₄的比表面积小、可见光吸收能力低、光生电子-空穴复合率高影响了其光催化性能。以邻氨基苯甲腈和尿素为原料,通过高温共聚改性制备高催化活性的g-C₃N₄-N光催化剂,研究g-C₃N₄-N在不同pH值、g-C₃N₄-N投加量和RhB溶液浓度条件下对RhB光催化降解的影响,并结合红外光谱、XRD、BET、UV-Vis对g-C₃N₄-N光催化降解RhB的机理和染料降解路径进行解析。结果表明,经共聚改性制备的碳化氮为类石墨型纯相g-C₃N₄-N,具有稳定的光催化活性、大的比表面积和多孔结构,在初始pH值为3时,加入50 mg的g-C₃N₄-N在可见光条件下光催化降解10 mg·L-1 的RhB可达到最好的光催化降解效果,RhB在暗反应30 min内的吸附去除率可达30%左右,120 min的去除率达到97.7%。在光催化作用下,g-C₃N₄-N将吸附在光催化剂表面的罗丹明B分子通过快速N-脱乙基过程形成DER、EER和AR等大分子中间体,它们在空穴与·OH和·O-₂作用下,共轭结构裂解、开环,生成丁二酸、间苯二酚、丙酸等小分子,脱除的乙基被逐步氧化为乙二醇,这些小分子可以被转化为CO₂和H₂O。     

石墨相氮化碳的制备条件优化用以提高其在可见光下的光催化活性

通过染料的光降解实验和敏感性数学分析探讨了石墨相氮化碳(g-C₃N₄)的制备条件与其稳定性和光催化活性之间的联系. 结果表明,相比于焙烧时间,焙烧温度的改变更为显著地影响了g-C₃N₄ 的光催化活性. 制备条件优化之后的g-C₃N₄在可见光照射下催化降解罗丹明B(RhB)的活性比未优化时提高了约100倍,归因于材料比表面积的增大和表面光生电子-空穴迁移速度的增强.     

基于W@WO3纳米薄膜光催化特性增强研究

采用无催化剂高温反应热蒸发和磁控溅射相结合的方法,在碳布上生长了W@WO_3纳米结构薄膜。通过XRD、SEM、XPS测试表明样品结构具有很好的结晶性,且W颗粒吸附在WO_3纳米薄膜上构成了欧姆结,可用于提高半导体材料的电荷分离效率。通过将样品放入罗丹明B溶液进行可见光照射5h,76%的RB可被降解,与降解效率为26%的WO_3纳米结构相比,经过W修饰后的样品光催化性能可得到大幅提升。实验利用碳布作为衬底生长出大比表面积纳米薄膜,可为了提供更多的光催化反应的活性位点。实验无需采用价格昂贵的贵金属修饰,也无需采用催化剂,可为低成本简易制备高质量的光催化材料提供有效制备方法,在污水等有机物的处理降解领域具有广阔的应用前景。     

MoO_(3-x)/PCN的原位合成及其增强光催化产氢性能的研究（英文）

本文通过简单的一步浸渍煅烧法原位合成了氧化钼纳米晶/聚合物氮化碳复合光催化剂,该不含铂基助催化剂的氧化钼修饰聚合物氮化碳光催化剂在可见光照射下表现出增强的光催化产氢性能,最高产氢速率为15.6μmol/h,是普通聚合物氮化碳样品的3倍以上.相应的结构与性能的分析表明,与后浸渍法不同,在原位生长过程中高分散的超小氧化钼纳米晶体与聚合物氮化碳之间形成了紧密的耦合界面结构,可见光产氢活性的提升源自高分散的超小氧化钼纳米晶与聚合物氮化碳之间形成的紧密界面,以及该界面结构形成的肖特基结带来的有效电荷载流子转移.     

MoO3-x/PCN的原位合成及其增强光催化产氢性能的研究

本文通过简单的一步浸渍煅烧法原位合成了氧化钼纳米晶/聚合物氮化碳复合光催化剂，该不含铂基助催化剂的氧化钼修饰聚合物氮化碳光催化剂在可见光照射下表现出增强的光催化产氢性能，最高产氢速率为15.6 μmol/h，是普通聚合物氮化碳样品的3倍以上. 相应的结构与性能的分析表明，与后浸渍法不同，在原位生长过程中高分散的超小氧化钼纳米晶体与聚合物氮化碳之间形成了紧密的耦合界面结构，可见光产氢活性的提升源自高分散的超小氧化钼纳米晶与聚合物氮化碳之间形成的紧密界面，以及该界面结构形成的肖特基结带来的有效电荷载流子转移.     

PbMoO4微晶的水热合成及光催化性能

以钼酸铵、硝酸铅为原料,采用水热法合成了纳米PbMoO₄光催化剂,并采用光还原处理对其进行表面载Ag修饰。借助X-射线粉末衍射（XRD）、扫描电镜（FE-SEM）和紫外-可见吸收光谱（UV-Vis）等测试手段对样品进行表征,并以罗丹明B为模型污染物,考察了纳米PbMoO₄光催化剂的催化活性,研究了样品的制备条件和表面载银对催化剂活性的影响。XRD分析结果表明,所得样品为四方晶系结构,且产物纯度高;样品的形貌分析和光催化活性实验结果表明,水热体系的pH值对产物的形貌和活性影响显著,且表面载银可显著提高催化剂的可见光催化活性。     

高稳定性Mn:ZnO/Mn2O3纳米复合光催化剂的制备及光催化特性

采用修饰的高分子网络凝胶法成功制备了Mn₂O₃复合Mn掺杂ZnO纳米复合光催化剂(Mn:ZnO/Mn₂O₃)，并基于模拟太阳光照射下罗丹明B(RhB)及亚甲基蓝(MB)染料的光降解研究了催化剂光催化降解有机染料的特性。X射线衍射，扫描电子显微镜及BET比表面积测试结果显示，微量(0.1 mol%)Mn掺杂再复合微量(0.2 mol%)Mn₂O₃后，Mn:ZnO/Mn₂O₃的颗粒尺寸减小且分散性提高，有效比表面积增大。紫外-可见光吸收光谱表明，相对于纯ZnO,Mn:ZnO/Mn₂O₃在可见光区域的光吸收能力明显提高。光致发光光谱表明微量Mn掺杂和微量Mn₂O₃复合促进了光生电子-空穴对的分离。结合X射线光电子能谱，发现可见光吸收能力和光生电子-空穴对分离率的提高源于催化剂表面氧空位的增加以及Mn:ZnO和Mn₂     

硼掺杂增强g-C3N4基单原子催化剂性能的第一性原理研究

单原子催化剂(SACs)以其最大的金属原子利用率和较高的催化活性而备受关注.本文提出了在Mn负载g-C₃N₄单层(Mn/g-C₃N₄)中进行B掺杂的方案来提升单原子催化剂的光催化活性,并利用第一性原理对Mn/B-g-C₃N₄单原子催化剂的晶体结构,电子结构,带边位置和光学性质进行计算.计算结果表明B掺杂具有较强的结构稳定性,带隙变小,同时带隙中出现杂质能级,导致吸收边向可见光区发生红移,提高了g-C₃N₄在太阳光下光吸收能力和光催化活性,研究结果为制备高效的g-C₃N₄基光催化SACs提供了理论指导.     

强冲击压缩条件下g-C3N4向β-C3N4直接转化

 为了合成出理论预言的具有致密结构的超硬材料C₃N₄,运用二级轻气炮加载和冲击回收实验技术,以富含N的g-C₃N₄为前驱物,在40~65 GPa压力下完成了冲击合成实验。在低于51 GPa压力时,X射线衍射分析表明,在回收样品中未发现有新相生成,说明g-C₃N₄是稳定的;而在51~65 GPa范围内,回收样品中有新相生成,与理论计算结果对照发现,新相为β-C₃N₄相,且不含其它结晶相。证实利用冲击合成方法将g-C₃N₄直接转化为单纯β-C₃N₄是可能的,对纯净的超硬相碳氮化合物的合成研究具有参考意义。     

Effect of multi-walled carbon nanotubes loaded with Ag nanoparticles on the photocatalytic degradation of rhodamine B under visible light irradiation

Multi-walled carbon nanotubes loaded with Ag nanoparticles (Ag/MWNTs) were prepared by two methods (direct photoreduction and thermal decomposition). The photocatalytic activity of Ag/MWNTs for the degradation of rhodamine B (RhB) under visible light irradiation was investigated in detail. The adsorption and photocatalytic activity tests indicated that the MWNTs served as both an adsorbent and a visible light photocatalyst. The photocatalytic activity of MWNTs was remarkably enhanced when the Ag nanoparticles were loaded on the surface of MWNTs. Moreover, the visible light photocatalytic activity of Ag/MWNTs depended on the synthetic route. On the basis of the experimental results, a possible visible light photocatalytic degradation mechanism was discussed.     

Fabrication and characterization of visible light-driven In<Subscript>2.77</Subscript>S<Subscript>4</Subscript>/In(OH)<Subscript>3</Subscript> composite photocatalysts with excellent redox performance

The In_2.77S₄ microspheres had been firstly fabricated by using polyethylene glycol (PEG) as the morphological modifier and then used to hybridize with In(OH)₃ nanocubes by a simply depositional method. The structure, optical properties, morphology, chemical compositions, and charge carrier behaviors of the as-prepared In_2.77S₄/In(OH)₃ composites were characterized, respectively. The methyl orange, tetracycline, rhodamine B, and Cr(VI) dilute solution were selected to evaluate their photocatalytic activities. Experimental results showed that In(OH)₃ nanocubes could improve the photocatalytic activity and recyclability of the In_2.77S₄ microspheres under the visible light irradiation. With the usage of In(OH)₃ increased, the photocatalytic efficiency of the hybrids was firstly increased and then decreased. When the mass ratios of In_2.77S₄ to In(OH)₃ were 6:2, it reached the maximum of 100% in 15 min for methyl orange, obviously higher than 67.4% of In_2.77S₄ and 1.1% of In(OH)₃. Meanwhile, it could also oxidize 85.6% of tetracycline in 20 min, 97.8% of rhodamine B in 7.5 min, and reduce 92.9% of Cr(VI) in 30 min under the visible light irradiation. Moreover, it could still degrade 91.7% of methyl orange solution after 3 cycles, which was much higher than 40.7% of In_2.77S₄ microspheres. In addition, the possible mechanism of enhancing photocatalytic properties was proposed.     

Synthesis,characterization and excellent photocatalytic activity of Ag/AgBr/MoO3 composite photocatalyst

A novel composite photocatalyst Ag/AgBr/MoO₃ was successfully synthesized via a simple precipitation method at room temperature. The obtained products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy and UV–vis diffuse reflectance spectroscopy in detail. The photocatalytic activity of the samples was evaluated by monitoring the degradation of rhodamine B (RhB) solution under visible-light irradiation. The results showed that the photocatalytic activity of Ag/AgBr/MoO₃ composite significantly enhanced and the degradation ratio of RhB reached 97.7 % after 15 min only. The excellent photocatalytic activity might be closely related to the large surface area, porosity structure and efficient separation of photoinduced electron–hole pairs. The possible reaction mechanism was also discussed.     

Sonocatalytic degradation of acid red B and rhodamine B catalyzed by nano-sized ZnO powder under ultrasonic irradiation

Nano-sized ZnO powder was introduced to act as the sonocatalyst after the treatment of high-temperature activation, and the ultrasound of low power was used as an irradiation source to induce nano-sized ZnO powder performing sonocatalytic degradation of acid red B and rhodamine B. At the same time, the effects of operational parameters such as solution pH value, initial concentration of dyestuff and addition amount of nano-sized ZnO powder have been examined in this paper. We found that the degradation ratios of acid red B and rhodamine B in the presence of nano-sized ZnO powder were much higher than that with only ultrasonic irradiation. However, the degradation ratio of acid red B was about two times higher than that of rhodamine B for the initial concentration of 10.0 mg/L, addition amount of 1.0 g/L nano-sized ZnO powder, solution acidity of pH 7.0 and 60 min irradiation experimental condition. The difference of the degradation ratios can be illustrated by the difference of chemical forms of acid red B and rhodamine B in aqueous solution and the surface properties of nano-sized ZnO particles. In addition, the researches on the kinetics of sonocatalytic reactions of acid red B and rhodamine B have also been performed and found to the follow pseudo first-order kinetics. All the experiments indicated that the sonocatalytic method in the presence of nano-sized ZnO powder was an advisable choice for the treatments of non- or low-transparent organic wastewaters in future.     

A Z-scheme CuO–ZnO–ZnS–CuS quaternary nanocomposite for solar-light-driven photocatalytic performance

A quaternary CuO–CuS–ZnO–ZnS nanocomposite was successfully synthesized via a facile microwave irradiation based on the preprepared ZnS and CuO nanoparticles. CuO–CuS–ZnO–ZnS nanocomposite was a porous photocatalyst, providing excellent adsorption performance. It was sensitive to both ultraviolet and visible light, moreover, the photoelectrochemical measurements confirmed that there was a high separation rate and low recombination rate of photo-generated charge carriers in the nanocomposite, endowing excellent photocatalytic activity in the sunlight. Under the simulated solar light irradiation, the removal efficiency of rhodamine B (RhB) pollutant (30 mg/L) over CuO–CuS–ZnO–ZnS nanocomposite was 33.98 and 2.90 times of pristine CuO and ZnS, respectively. The outstandingt photocatalytic performance was attributed to Z-scheme charge transfer path.     

TiO2 nanosized powders controlling by ultrasound sol-gel reaction

We studied that anatase-TiO2 powders prepared from sol-gel process of titanium tetra-isopropoxide (TTIP) were developed under ultrasonic irradiation with different frequency of 28, 45 and 100 kHz. The irradiated ultrasound (US) was controlled by using semi-cylindrical reflection plate that was placed onto the vicinity of reaction vessel. The focused US influenced the reduction of particles size and increased the surface area of resultant nanosized TiO2 powders. We also examined photodegradation of rhodamine 640 dye (Rh-640) solution by the resultant TiO2 under UV light exposure. It was observed that low frequency for TiO2 photocatalyst preparation and low calcination temperature were more affected onto the photodegradation of the dye.     

圆盘状Bi2WO6-BiPO4异质结的水热合成及光催化性能 (cited: 1)

采用水热法制备Bi₂WO₆-BiPO₄异质结光催化剂．利用模拟太阳光照射下的罗丹明B降解实验评价了Bi₂WO₆-BiPO₄复合物的光催化性能．结果表明,Bi₂WO₆-BiPO₄光催化活性比Bi₂WO₆和BiPO₄高得多．当Bi₂WO₆与BiPO₄的摩尔比为1:1时复合光催化剂对罗丹明B的降解率最高．Bi₂WO₆-BiPO₄催化活性增强主要归结为两者之间形成了有效的异质结结构,其内建电场能够促进光生载流子的分离．同时,Bi₂WO₆的加入增强了其对可见光的吸收．研究表明O₂· ^-和h⁺在光催化降解过程中是主要的活性物种     

强悬浮性纳米TiO2的制备、表征及光催化活性研究Ⅱ.光催化活性研究

将甲基橙溶液作为模拟废水,在紫外灯照射下,通过测量甲基橙溶液在470nm处吸光度的变化,考察了热分解制备纳米TiO2后处理过程中采用硅油淬火改性和自然冷却所得产物的光催化活性,并初步分析了两者光催化甲基橙的机理和在35min内的降解率和动力学反应过程。结果表明：两者均具有良好的光催化降解效果,且活性差别不大。但经硅油淬火改性的纳米TiO2因在水中具有强悬浮性,可更为有效地利用外部光源在工业废水的表层降解有害成分。