Bi基复合材料的制备及其可见光催化性能研究

发布时间：2018-05-01 08:24

本文选题：PVP + BiOBr　；参考：《湘潭大学》2017年硕士论文

【摘要】：Bi系半导体光催化材料因其独特的结构,合适的禁带宽度而具有良好的光催化活性,受到广大研究者关注。然而对于纯相Bi系光催化材料而言,其易发生光腐蚀现象、电子空穴复合率高、难以回收等缺点制约了其在实际工业中的应用和发展。本文选取化学性质稳定、禁带宽度适中、吸光范围广及环境友好的BiFeO_3及BiOBr为研究对象,并针对其缺点,以性能为导向进行了一系列适当的改性。具体开展的主要工作及研究结果如下:(1)采用PVP辅助溶剂热法成功制备了分散均匀的空心微球状BiOBr~-海泡石复合光催化剂(PVP/BiOBr/AS)。利用SEM、XRD、FTIR、XPS、UV-Vis等表征技术对其形貌特征、晶相结构、元素价态、吸光性能等进行了测试分析,结果表明改性后的复合催化剂团聚现象降低,光吸收性能增加,电子空穴复合率也显著降低。(2)以罗丹明B(RhB)为目标污染物评价了不同海泡石含量的PVP/BiOBr/AS复合光催化剂的催化活性,优选出海泡石最佳掺杂量为6%,光催化降解RhB120min时,脱色率100%,TOC的去除率为75.3%,明显优于纯相BiOBr。光催化降解RhB的最佳反应条件:催化剂投加量为1.0g/L,溶液初始浓度为10mg/L,溶液的初始pH为5。以最佳配比的PVP/BiOBr/AS(6%)复合光催化剂降解双氯芬酸钠,表现出良好的催化性能,表明复合催化剂适用范围较广。(3)采用水热法制备了异质结结构的斜方六面体BiFeO_3/CdS复合光催化剂。利用SEM、XRD、BET、UV-Vis等表征技术对其形貌特征、晶相结构、比表面积、吸光性能等进行了测试分析。以罗丹明b(RhB)为目标污染物评价了不同CdS含量的BiFeO_3/CdS复合光催化剂的催化活性,结果表明BiFeO_3/CdS复合光催化剂催化活性和稳定性都得到了提升,在一定程度上解决了BiFeO_3光催化性能不够高和CdS易光腐蚀等问题。(4)进行自由基捕获实验考察反应过程中活性物种。结果表明:O2·-、h+、·OH均参与PVP/BiOBr/AS降解有机物的过程,其中O2·-起主要作用。在BiFeO_3/CdS光催化降解RhB过程中,O2·-是主要活性物种。(5)由GC-MS和UV-Vis DRS测试分析可知,在PVP/BiOBr/AS催化剂降解RhB过程中,RhB首先发生脱乙基过程,而后在自由基的作用下发生苯环裂解。生成了化合物十六酸、油酸和对二苯酚,随着反应时间的增加,自由基逐步将污染物降解成己二酸、戊二酸等小分子化合物,最后被矿化成CO2、H2O。
[Abstract]:Bi-based semiconductor photocatalytic materials have good photocatalytic activity due to their unique structure and suitable band gap. However, for the pure Bi system photocatalytic materials, the photocorrosion is easy to occur, the electron hole recombination rate is high, and it is difficult to recover, which restricts its application and development in practical industry. In this paper, BiFeO_3 and BiOBr, which have stable chemical properties, moderate bandgap, wide absorptivity and friendly environment, are selected as research objects, and a series of performance oriented modification are carried out according to their shortcomings. The main work and results are as follows: (1) PVP assisted solvothermal method was used to successfully prepare a well-dispersed hollow microsphere BiOBr-sepiolite composite photocatalyst (PVP / BiOBr-ASN). The morphology, crystal structure, elemental valence state and absorptivity of the modified composite catalysts were measured and analyzed by means of the SEMP-XRDX / FTRDX / XPS UV-Vis technique. The results showed that the agglomeration of the modified composite catalysts was decreased, and the photoabsorption properties of the modified catalysts were increased. The electron hole recombination rate was also significantly reduced. (2) the catalytic activity of PVP/BiOBr/AS composite photocatalyst with different sepiolite content was evaluated by using Rhodamine Bhh RhB) as the target pollutant. The optimum doping amount of sepiolite was 6 and the photocatalytic degradation of RhB120min was obtained. The removal rate of TOC was 75.3%, which was better than that of pure phase BiOBr. The optimum reaction conditions for photocatalytic degradation of RhB were as follows: the dosage of catalyst was 1.0 g / L, the initial concentration of the solution was 10 mg / L, and the initial pH of the solution was 5. The photocatalytic degradation of diclofenac sodium by PVP / BiOBr-AS6) composite photocatalyst shows good catalytic performance, indicating that the composite catalyst is suitable for a wide range. (3) Heterojunction structure oblique hexahedron BiFeO_3/CdS composite photocatalyst has been prepared by hydrothermal method. The morphology, crystal phase structure, specific surface area and absorptivity were measured and analyzed by means of SEMX (XRDX) BET-UV-Vis. The catalytic activity of BiFeO_3/CdS composite photocatalyst with different CdS content was evaluated by using Rhodamine CdS as the target pollutant. The results showed that the catalytic activity and stability of BiFeO_3/CdS composite photocatalyst were improved. To some extent, the problem of BiFeO_3 photocatalysis is not high enough and CdS is easy to corrode. 4) the free radical trapping experiment is carried out to investigate the active species in the reaction process. The results showed that both O _ 2 -O _ 2 and OH were involved in the degradation of organic matter by PVP/BiOBr/AS, and O _ 2-played a major role in the degradation of organic matter. In the process of BiFeO_3/CdS photocatalytic degradation of RhB, O2- is the main active species. According to the analysis of GC-MS and UV-Vis DRS, it can be seen that the deethylation process occurs first and then benzene ring cleavage occurs under the action of free radical in the degradation of RhB by PVP/BiOBr/AS catalyst. The compounds hexadecanoic acid, oleic acid and p-diphenol were formed. With the increase of reaction time, the pollutants were gradually degraded into adipic acid, glutaric acid and other small molecular compounds, which were mineralized to CO _ 2H _ 2O.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703;TB33

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