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层状双金属(氢)氧化物/碳基复合材料的制备及其光催化应用
论文作者:童鞋论文网  论文来源:www.txlunwenw.com  发布时间:2019/11/1 9:08:34  

摘要:半导体诱导光催化技术在处理环境污染方面备受关注,但是,光生电子-空穴对的高重组率、材料的光腐蚀以及回收利用等问题严重限制了其实际应用。本文以层状双金属氢氧化物(LDH)和双金属氧化物(MMO)为光催化主体,石墨烯为载体材料制备了高效可见光光催化剂,并通过XRD、XPS、FTIR、Raman、SEM、TEM、BET等测试探究了复合光催化剂的结构和形貌;同时采用UV-Vis DRS、PL、EIS和瞬态光电流研究了催化剂的光电性能并提出了相应的光催化机理。主要研究内容如下:

(1) 采用简单的水热法成功制备了可磁分离的NiAl LDH/Fe3O4-RGO复合光催化剂。其结构和形貌的表征表明石墨烯的加入促进了更小、更薄的NiAl LDH纳米片的原位生长;同时,Fe3O4纳米粒子(NPs)均匀分布于石墨烯片层上。通过对NiAl LDH/Fe3O4-RGO催化剂的光催化性能检测,证明了引入石墨烯有利于该复合催化剂获得更大的比表面积,同时提供了更多的反应活性位点。当石墨烯含量为25 wt %,在150 min可见光照射下,NiAl LDH/Fe3O4-RGO复合光催化剂的降解效率可达到91.36 %。相比较于NiAl LDH纯样,石墨烯和Fe3O4 NPs的存在有效抑制电荷重组和增强光吸收能力;与此同时,Fe3O4 NPs的存在使得该复合光催化剂能够轻松地实现可磁分离和循环利用,大大提高了催化剂的再生和重复利用效率。

(2) 采用低温水热结合煅烧法将ZnAlLDH/GO前驱体成功转化为ZnAl MMO/RGO纳米杂化复合物。高温煅烧过程中,将石墨烯还原的同时,其表面负载的ZnAl LDH转化成均匀分布的ZnO/ZnAl2O4异质结,这些ZnO/ZnAl2O4纳米粒子均匀地固载于石墨烯片层。通过可见光催化降解CIP溶液来评估其光催化性能,当石墨烯含量为20 wt %,在120 min可见光照射下,ZnAl MMO/RGO纳米杂化复合物的降解效率可达90.58 %。该复合物光催化性能的提升主要归因于ZnO/ZnAl2O4异质结和石墨烯之间的界面相互作用,引起了宽泛的可见光响应区域、出色的光生载流子的分离效率。通过对其光电性能的研究证实了上述结论并且对可能的光催化机理做了相应的探究。

Semiconductor-mediated photocatalysis hasattracted much attention in the treatment of environmental pollution. However,the high recombination rate of photo-generated electron-hole pairs,photo-corrosion and poor recycling of materials have seriously limited theirpractical application. In this paper, layered doubled hydrogen oxides (LDH) andmixed metal oxides (MMO) were used as the host of photocatalyst and graphenewas used as the substract to prepare high efficiency visible-light-inducedphotocatalysts. The structure and morphology of the composite photocatalystswere characterized by XRD, XPS, FTIR, Raman, SEM, TEM and BET etc. Meanwhile,the optical, electrical properties and photocatalysis mechanism ofphotocatalysts were studied by UV-Vis DRS, PL, EIS and transient photocurrent.The main studies are as follows:

(1) Magnetically separable NiAlLDH/Fe3O4-RGO photocatalyst was successfully prepared by a simple hydrothermalmethod. The characterization results of the structure and morphologiesindicated that the addition of graphene promoted the in-situ growth of smallerand thinner NiAl LDH nanosheets. Meanwhile, Fe3O4 nanoparticles (NPs) wereevenly distributed on the graphene sheets. NiAl LDH/Fe3O4-RGO showed enhancedthe photocatalytic performance, which suggested that the introduction ofgraphene afforded the composite larger specific surface areas and provided morereactive sites. The degradation efficiency of NiAl LDH/Fe3O4-RGO photocatalystreached 91.36 % when the content of graphene is 25 wt % after 150 min ofvisible-light irradiation. Compared with pure NiAl LDH, the presence ofgraphene and Fe3O4 NPs effectively inhibited charge recombination and enhancedlight absorption. Besides, the photocatalysts can be easily separated andrecycled under an external magnetic field due to the existence of Fe3O4 NPs,which increases the regeneration and reusability of catalysts.

(2) The ZnAl LDH/GO precursor was successfullyconverted to ZnAl MMO/RGO nanohybrid composites by a facile hydrothermal methodcombined with a calcination process. The thermal treatment enablessimultaneously the formation of ZnO/ZnAl2O4 heterogeneous structure, which areuniformly decorated on the surface of graphene, and the reduction of grapheneoxide. The photocatalytic performance of the ZnAl MMO/RGO nanohybrid compositecan reach 90.58 % after 120 min of visible-light irradiation when the contentof graphene is 20 wt %. The improvement of the photocatalytic activity ofnanocomposite is attributed to the interfacial interaction between theZnO/ZnAl2O4 heterojunction and graphene, which leads to the broadenedvisible-light-response region and excellent separation efficiency ofphoto-induced carriers. The above mentioned conclusions have been confirmedthrough studying the optical and electrical properties of the composite.Besides, the possible photocatalytic mechanism has been explored accordingly.

关键词:光催化;层状双金属(氢)氧化物;石墨烯

photocatalysis; layered doubled (hydrogen)oxides; graphene

上一篇:基于N-炔磺酰胺的氮杂环合成     下一篇:三维石墨烯负载Pd催化剂的制备及加氢性能研究
 
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