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硫化锌镉复合材料的制备及其光催化降解有机染料性能研究
论文作者:童鞋论文网  论文来源:www.txlunwenw.com  发布时间:2019/9/11 8:19:56  

摘要:具有合适带隙等优良性能的金属硫化物可作为在可见光下去降解污染物的良好光催化剂候选物。其中,CdS由于窄带隙使得其对可见光区域的响应更加灵敏,引起了人们的广泛关注。但在可见光照射下,其电荷重组率高,光腐蚀严重,在很大程度上抑制了CdS的应用。另一方面,ZnS的带隙约为3.66eV,具有显著的氧化还原能力和耐久性,但不能有效利用可见光。为了克服上述问题,CdS和ZnS结合成 ZnxCd1-xS光催化剂是一种可行的方法,因为CdS与ZnS具有相似的配位模式,金属原子可以在同一晶格中相互取代。ZnCdS克服了CdS弱氧化性和易腐蚀性,光吸收边缘进入可见光区。

光催化研究者的目光被铋系化合物具有良好的光吸收性能和稳定性等催化优点深深吸引。本论文以铋系物为载体与ZnCdS半导体材料复合,三种不同的半导体光催化剂被成功合成,并且利用XRD、SEM、TEM、DRS、Raman、PL和瞬态光电流测试对材料的结构、形貌和电化学响应进行了评价。研究了三种与ZnCdS复合的光催化剂对孔雀石绿(MG)的光催化活性。阐明了ZnCdS/BiOBr,ZnCdS/BiPO4和ZnCdS/Bi2WO6材料的光催化机理。主要的研究内容如下:

(1)本实验采用三步法制备ZnCdS/BiPO4复合材料。利用XRD、SEM、TEM、Raman、PL、DRS表征光催化剂形貌和结构。显示粒径约20~80nm的ZnCdS颗粒均匀的负载在棒状的BiPO4上。实验降解以MG为污染物,研究评价ZnCdS/BiPO4复合材料的光催化活性和降解的稳定性。实验结果看出降解速率快效果佳的是1.2-ZnCdS/BiPO4复合材料,表明1.2质量比的ZnCdS/BiPO4光催化活性最高,60min降解MG的效率约为88%,降解率是ZnCdS的1.34倍。可能由于ZnCdS颗粒的掺杂增大了光催化的表面积等原因。ZnCdS/BiPO4光催化降解过程中的主要活性物种通过自由基捕获实验检测。探究ZnCdS/BiPO4复合材料的光催化机理。

(2)本实验采用三步法制备ZnCdS/BiOBr复合材料。粒径约20~80nm的ZnCdS颗粒均匀的负载在四方形BiOBr的表面。利用XRD、SEM、TEM、Raman、PL、DRS表征光催化剂形貌和结构。以MG作为污染物被降解,研究评价ZnCdS/BiOBr复合材料的光催化活性和降解的稳定性。ZnCdS/BiOBr光催化降解过程中的主要活性物种通过自由基捕获实验检测。探究ZnCdS/BiOBr复合材料的光催化机理。复合后的光催化剂ZnCdS/BiOBr由于促进光生电子-空穴对的分离,增大光响应面积,抑制光生电子-空穴对的重组等,大大增加了MG的降解效果。

(3)本实验采用三步法制备ZnCdS/Bi2WO6复合材料。利用XRD、SEM、TEM、Raman、PL、DRS表征光催化剂形貌和结构。粒径约20~80nm的ZnCdS颗粒均匀的负载微球Bi2WO6面上。在可见光照射下,实验降解以MG为污染物,研究评价ZnCdS/Bi2WO6复合材料的光催化活性和降解的稳定性。1.3-ZnCdS/Bi2WO6光催化剂降解MG的速率快效果佳。50min降解了94%的MG。复合光催化剂的降解效率在四个循环周期后为90%,说明1.3-ZnCdS/Bi2WO6材料稳定性较好。ZnCdS/Bi2WO6光催化降解过程中的主要活性物种通过自由基捕获实验检测。探究ZnCdS/Bi2WO6复合材料的光催化机理。

Metal sulfides are good candidates forvisible light photocatalysts because of their suitable band gap and improvedcatalytic function. Among them, CdS is more sensitive to the visible lightregion due to the narrow band gap, which has caused widespread concern.However, under visible light irradiation, the charge recombination rate is highand the light corrosion is severe, which greatly inhibits the application ofCdS. On the other hand, ZnS has a band gap of about 3.66 eV, which hasremarkable redox ability and durability, but cannot effectively utilize visiblelight. In order to overcome the above problems, the combination of CdS and ZnSinto a ZnxCd1-xS photocatalyst is a feasible method because CdS has a similarcoordination mode with ZnS, and metal atoms can be substituted with each otherin the same crystal lattice. ZnCdS overcomes the weak oxidative and corrosivenature of CdS, and the light absorption edge enters the visible region.

Lanthanide compounds have good lightabsorption properties and stability, attracting the attention of photocatalystresearchers. In this thesis, different composite semiconductor photocatalystswere prepared by using lanthanide as carrier and zinc cadmium sulfidesemiconductor photocatalyst, and the structure and shape of the material weretested by XRD, SEM, TEM, DRS, Raman, PL and transient photocurrent. Theappearance and electrochemical response were evaluated. The photocatalyticactivity of photocatalysts on MG was investigated. The photocatalytic mechanismof the photocatalyst was clarified. A new type of photocatalyst is provided tomore effectively utilize solar energy to degrade organic pollutants. The mainresearch contents are as follows:

(1) A ZnCdS/BiPO4 nanocompositephotocatalyst was prepared by a three-step method. The morphology and structureof the photocatalyst were characterized by XRD, SEM, TEM, Raman, PL and DRS. Itwas shown that ZnCdS particles having a particle diameter of about 20 to 80 nmwere uniformly supported on the rod-shaped BiPO4. Using MG as a pollutant, thephotocatalytic activity and degradation stability of the compositephotocatalyst were evaluated. The results showed that the degradation of1.2-ZnCdS/BiPO4 photocatalyst was the best and the photocatalytic activity wasthe highest. The efficiency of degradation of MG in 60 min was about 88%, andthe degradation rate was 1.34 times that of ZnCdS. It is possible that thedoping of ZnCdS particles increases the surface area of photocatalysis and thelike. The main active species in the photocatalytic degradation process weredetected by free radical trapping experiments, and the photocatalytic mechanismof semiconductor photocatalytic materials was explored.

(2) A ZnCdS/BiOBr nanocompositephotocatalyst was prepared by a three-step method. The ZnCdS particles having aparticle size of about 20 to 80 nm are uniformly supported on the surface ofthe tetragonal BiOBr. The morphology and structure of the photocatalyst werecharacterized by XRD, SEM, TEM, Raman, PL and DRS. The photocatalytic activityand degradation stability of the composite photocatalyst were evaluated byusing the dye malachite green (MG) as a pollutant. The main active species inthe photocatalytic degradation process were detected by free radical trappingexperiments, and the photocatalytic mechanism of semiconductor photocatalyticmaterials was explored. The composite photocatalyst greatly enhances thedegradation effect of MG by promoting separation of photogeneratedelectron-hole pairs, suppressing recombination of photogenerated electron-holepairs, and increasing photoreaction area.

(3) A ZnCdS/Bi2WO6 nanocompositephotocatalyst was prepared by a three-step method. The morphology and structureof the photocatalyst were characterized by XRD, SEM, TEM, Raman, PL and DRS.

关键词:硫化锌镉;磷酸铋;溴氧化铋;钨酸铋;光催化活性

ZnCdS; Bi2WO6; BiOBr; BiPO4; Photocatalyticactivity

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