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硫化镉基复合材料的制备及其光催化性能调控研究

作者:优质期刊论文发表网  来源:www.yzqkw.com  发布时间:2019/10/26 14:08:04  

摘要:在现代经济社会快速发展的同时,环境污染与能源危机问题日渐严峻。众多学者发现,光催化半导体材料因其独特的优势可被应用于环境污染治理、新能源开发等众多方向。但由于传统的半导体材料如TiO2等,对太阳光响应范围较小,极大地限制了光催化技术的发展与应用。如何设计出新型高效、环境友好、价格低廉的半导体材料是目前光催化领域中的研究热点。

硫化镉作为众多半导体中光电化学性质较为优异的一种材料,其因拥有合适的禁带宽度、较高的量子效率、较强的光催化活性而展示出巨大的应用前景,获得学者们的广泛研究。但同时它还存在光生载流子易复合、材料易光腐蚀等缺点。本论文选取不同半导体纳米材料与硫化镉复合,通过构建异质结的方法对其进行改性,以求达到增强光催化活性、提高可见光利用率的目的,并探讨其在光催化降解和光解水产氢方向的应用性能。本课题的主要研究内容如下:

(1)以水热法制备BiOBr纳米片及CdS纳米颗粒,通过超声浸渍法将两种半导体进行复合,得到新型的BiOBr/CdS纳米复合材料。并以孔雀石绿(MG)为模拟污染物,对复合材料的光催化降解活性及稳定性进行测试。发现复合材料在100min内对MG的最高降解率达到99 %,同时通过自由基捕获实验探讨复合材料在可见光下的反应机制。

(2)先以溶剂热法合成得到长约1 mm的CdS纳米棒,再利用原位水热法在CdS表面生长MnWO4纳米颗粒,制备得到MnWO4/CdS纳米复合材料。在可见光照射下,复合材料对Cr(Ⅵ)的还原率最高达到98 %,且在五组循环实验后仍然保持在90 %的还原率。通过MnWO4与CdS间的协同效应,有效抑制了材料所产生的光生载流子的复合,增强了复合材料的光催化活性,使其在可见光照射下表现出对Cr(Ⅵ)良好的还原性能以及稳定性。

(3)通过溶剂热法以及水热法分别制备CdS和CdWO4纳米材料,再通过超声浸渍法合成CdWO4/CdS复合材料。在以孔雀石绿为目标污染物的降解实验中,所得到的复合材料在可见光照射下,对MG的降解率最高达到97 %,五次循环实验后仍保持在86 %,展现出优异的光催化活性以及稳定性。同时在复合材料的平均产氢速率最高达到2395.98μmol/h/g,远高于CdS的657.67 μmol/h/g。CdS和CdWO4之间产生的Z型异质结保留了材料的氧化还原能力,抑制了光生载流子的复合,有效增强了复合材料的光催化活性。

(4)采用溶剂热法以及原位水热法制备得到CoWO4/CdS复合材料,测试其结构、形貌、光电化学等性质。在可见光照射下,复合材料对MG的降解率最高达到97 %,3 h内的平均产氢速率最高达到15.91mmol/h/g,并保持着良好的光催化稳定性。这是由于所得到的复合材料的光生电荷迁移遵循Z型异质结,在CdS的基础上有效拓宽了复合材料的光响应范围,增强了对可见光的吸收能力以及有效抑制了光生载流子的复合率。

(5)先通过溶剂热法合成CdS纳米棒,再利用原位水热法在CdS纳米棒上负载ZnWO4纳米颗粒,制备得到ZnWO4/CdS复合材料。所得复合材料在3 h内的平均产氢速率最高达到79.27 mmol/h/g,并且表现出远优于CdS的光催化稳定性。这是由于通过ZnWO4和CdS亲密接触,有效地分离了CdS所产生的光生载流子,提高了光生电子的寿命,使复合材料获得优异的光解水产氢性能。

With the rapid development of contemporaryeconomy and society, environmental pollution and energy crisis are becomingmore and more serious. It is found that the photocatalytic semiconductors whichhave unique advantages can be applied in many fields like environmentalpollution, new energy development and so on. However, the confinedphotoresponse range for solar light of traditional semiconductors such as TiO2limits the development and application of photocatalytic materials. Therefore,designing novel, efficiency, environment-friendly and low-cost semiconductorshave become hotspots in the photocatalytic field.

Cadmium sulphide with more excellentphotochemical properties in multitudinous semiconductors, has been widelyinvestigated, the suitable band gap, high quantum efficiency and strongphotocatalytic activity. Meanwhile, CdS also has the defects of easyrecombination of photogenerated carriers and photocorrosion. In this paper,different semiconductors were selected to couple with CdS for modifying byconstructing heterojunction, in order to enhance the photocatalytic activityand visible-light utilization. Moreover, the performance of photocatalyticdegradation and hydrogen production was measured and discussed. The maincontents of this study are as follows:

(1) BiOBr nanosheets and CdS nanoparticleswere prepared by hydrothermal method. The novel BiOBr/ CdS composites wasobtained by ultrasonic impregnation. The malachite green (MG) as the simulatedpollutant was used to measure the performance and stability of photocatalyticdegradation for composites. It was found that the highest degradability of MGachieved 99% within 100 min, and the mechanism of composites undervisible-light irradiation was investigated by radical-trapping experiments.

(2) CdS nanorods with the length of about 1mm were prepared by solvothermal method, and the MnWO4 nanoparticles grow onthe surface of CdS by in-situ hydrothermal method to synthetize the MnWO4/CdScomposites. Under visible-light irradiation, the highest reductionrate of Cr(Ⅵ)with composites was up to 98 %, and still maintained with 90 % at fifth cycleexperiment. The synergistic effect between MnWO4 and CdS suppresses therecombination of photogenerated carriers effectively and enhances thephotocatalytic activity of composites, causing that MnWO4/CdS compositesexhibit the outstanding performance and stability of Cr(Ⅵ) reduction undervisible-light irradiation.

(3) CdS and CdWO4 composites were preparedby solvothermal method and hydrothermal method, and the CdWO4/CdS compositeswas synthesized by ultrasonic immersion method. The malachite green as targetpollutant was degraded by CdWO4/CdS composites under visible-light irradiation.The highest degradation rate was up to 97 %, and still maintained with 90 % atfifth cycle experiment, demonstrating the excellent photocatalytic activity andstability. Meanwhile, average photocatalytic H2 production rate of compositesreached 2395.98 μmol/h/g highest, which was much higher than that of CdS(657.67 μmol/h/g). The Z-scheme heterojunction between CdS and CdWO4 remainsthe redox ability of composites, suppresses the recombination of photogeneratedcarriers effectively and enhances the photocatalytic activity of composites.

(4) CoWO4/CdS composites were prepared bysolvothermal method and in-situ hydrothermal method, and the structure,morphology and photochemical properties of composites were measured. Undervisible-light irradiation, the highest degradation rate of MG reached 97 %,while the average photocatalytic H2 production rate reached 15.91 mmol/h/g in 3h and maintained good photocatalytic stability. Because the migration ofphotogenerated carriers follows Z-scheme heterojunction, which enhances thephotoabsorption ability for visible-light and recombination rate of photogeneratedcarriers. Moreover, the photoresponse range of composites is widenedeffectively on the basis of CdS.

关键词:硫化镉;光催化降解;光催化产氢;异质结

Cadmium sulfide; Photocatalyticdegradation; Photocatalytic hydrogen production; Heterojunction

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