钛基二元复合氧化物的制备及其光催化性能研究

发布时间：2018-10-05 06:43

【摘要】：二氧化钛光催化技术能够利用太阳能缓解环境和能源问题,是一种很有前景的半导体材料,得到了广泛的关注和应用。复合型光催化材料的开发对促进半导体光催化技术在太阳能利用率中具有重要的科学意义。本论文以TiO_2为基体,先后采用模板-溶剂热法、溶剂热法和原位-溶剂热法合成了二元复合氧化物TiO_2/SiO_2,TiO_2/Bi_2WO_6和TiO_2/Bi_(3.64)Mo_(0.36)O_(6.55)光催化剂,并对材料的形貌和微观结构对光催化性能的影响进行了系统研究。通过光催化降解污染物评估催化剂的光催化活性,同时探讨了自由基捕获实验、电子自旋共振技术、荧光光谱和光电化学测试,提出了可能的光催化机理。首先,通过模板-溶剂热法合成了二元复合氧化物TiO_2/SiO_2光催化剂。以罗丹明B(RhB)为目标污染物,评价了所制备光催化剂在紫外光和可见光下降解有机污染物的应用,以提高太阳能的利用率。在优化条件下,TS2(TS2代表着钛硅摩尔比为1:1)可见光降解罗丹明B的表观速率常数是纯TiO_2的33倍多,是商用TiO_2(P25)的6倍多;在紫外光下是纯TiO_2的5倍多,是P25的1倍多。在可见光光照40 min的条件下,TS2对甲基橙降解率只有11.6%,复合光催化剂TS2对罗丹明B光催化活性最好。TS2在可见光照射下重复使用5次后降解率只降低9%,说明该催化剂表现出良好的稳定性。因此,光催化剂TS2对罗丹明B光催化降解具有高效选择性。在光催化反应液中分别加入对苯醌(BQ)或乙二胺四乙酸二钠(EDTA-2Na),TS2对RhB的降解率分别为19.0%或37.8%。结果证实活性物种超氧自由基(·O_2-)和空穴(h+)在降解RhB中扮演重要的角色。然而,当加入叔丁醇(TBA)时,TS2对RhB的降解率为95.7%,说明羟基自由基(·OH)不是主要的活性物种。其次,采用溶剂热法设计合成了TiO_2/Bi_2WO_6复合材料。通过在可见光下降解两种不同类型的污染物(罗丹明B(RhB)、四环素(TC)和环丙沙星(CIP))来拓宽复合物的实际应用。在可见光下降解RhB溶液对应的ln(C0/C)具有很好的拟合,表明遵循一级动力学。TB2(TiO_2与Bi_2WO_6的摩尔比为1:1)的速率常数为0.1598min-1,高于Bi_2WO_6(0.0996 min-1),TiO_2(0.0165 min-1)和P25(0.0255 min-1)。TB2催化剂在可见光下照射40 min,TC的降解率为63.3%,而纯Bi_2WO_6仅为33.9%,纯TiO_2仅为56.9%。制备的复合物在可见光照射下,增强了光催化降解RhB,TC和CIP催化活性,归因于半导体之间的异质界面的光生电子/空穴复合率低的影响。TiO_2/Bi_2WO_6复合物的荧光强度低于纯Bi_2WO_6,表明TiO_2/Bi_2WO_6复合物的形成抑制电子和空穴的复合。光电化学的光电流和阻抗测试,也表明光生载流子的快速转移。电子自旋共振技术(ESR)结果显示,超氧自由基是主要的活性物种,这与自由基捕获实验吻合,在此基础上提出可能的光催化机理。最后,采用原位-溶剂热法以不同的TiO_2的负载量制备TiO_2/Bi_(3.64)Mo_(0.36)O_(6.55)复合光催化剂。Bi_(3.64)Mo_(0.36)O_(6.55)在光照30 min时降解率达到85.8%,但是,引入TiO_2后,TiO_2(15wt%)/Bi_(3.64)Mo_(0.36)O_(6.55)(记为TBMO_3)复合物的催化活性显著提高。光催化剂光催化降解罗丹明B溶液为一级动力学反应。TBMO_3的速率常数为0.2068 min-1,分别是Bi_(3.64)Mo_(0.36)O_(6.55),P25和TiO_2的4.5,10和94倍。通过充分利用TiO_2的高比表面积(134.24 m2·g-1),对该复合材料的比表面积和多孔性进行了探究,证明了比表面积在复合型材料的光催化活性中体现出显著的优势。结果表明,与Bi_(3.64)Mo_(0.36)O_(6.55)(6.77 ns)比较,TBMO_3具有较短的平均寿命为4.61 ns,更高的光催化活性可以归因于有效的电荷转移和分离。荧光光谱测试进一步证明了通过TiO_2和Bi_(3.64)Mo_(0.36)O_(6.55)的协同作用可以有效的实现光生载流子的分离和输运,可能归属于Z-型光催化机理。TiO_2/Bi_(3.64)Mo_(0.36)O_(6.55)复合物具有较好的稳定性,这表明复合材料可以为制备新型高效的光催化剂在水净化和环境处理应用中提供有效的策略。
[Abstract]:Titanium dioxide photocatalysis technology can utilize solar energy to alleviate environment and energy problem, it is a promising semiconductor material, and has gained wide attention and application. The development of composite photocatalytic material has important scientific significance in promoting semiconductor photocatalysis technology in solar energy utilization. In this paper, TiO _ 2/ SiO _ 2, TiO _ 2/ Bi _ 2WO _ 6 and TiO _ 2/ Bi _ (3.64) Mo _ (0.036) O _ (6.55) photocatalysts were synthesized by template-solvent thermal method, solvent thermal method and in situ-solvent thermal method, and the effects of morphology and microstructure on photocatalytic performance were systematically studied. The photocatalytic activity of the catalyst was evaluated by photocatalytic degradation, and the possible mechanisms of photoionization were also discussed. First, the binary composite oxide TiO _ 2/ SiO _ 2 photocatalyst was synthesized by template-solvent thermal method. RhB (RhB) is used as the target pollutant, and the application of the prepared photocatalyst in ultraviolet and visible light degradation and organic pollutants is evaluated to improve the utilization rate of solar energy. Under the optimum conditions, TS2 (TS2 stands for the molar ratio of titanium to silicon: 1: 1), the apparent rate constant of visible light degradation is more than 33 times of pure TiO _ 2, which is 6 times more than that of commercial TiO _ 2 (P25); under the ultraviolet light is more than 5 times of pure TiO _ 2, which is more than 1 times of P25. The degradation rate of TS2 to methyl orange was only 11. 6% under the condition of 40 min of visible light illumination. The photocatalytic activity of TS2 was the best. After repeated use of TS2 for 5 times under visible light irradiation, the degradation rate was only reduced by 9%, indicating that the catalyst exhibited good stability. Therefore, the photocatalyst TS2 has high-efficiency selectivity to the photocatalytic degradation of the RhB B. The degradation rates of BQ or EDTA-2Na and TS2 to RhB were 19. 0% or 37. 8%, respectively. The results confirmed that the active species super-oxygen free radical (路 O _ 2-) and hole (h +) play an important role in the degradation of RhB. However, when tert-butanol (TBA) was added, the degradation rate of TS2 to RhB was 95.7%, indicating that hydroxyl radical (路 OH) was not the main active species. Secondly, TiO _ 2/ Bi _ 2WO _ 6 composites were synthesized by solvent thermal method. The practical application of the complex was widened by two different types of pollutants (RhB (RhB), tetracycline (TC) and Cioxacin (CIP) in the visible light reduction. A good fit is given to the solution (C0/ C) corresponding to the RhB solution of the visible light falling solution, which shows that the first-order kinetics is observed. The rate constant of TB2 (molar ratio of TiO _ 2 to Bi _ 2WO _ 6 was 1: 1) was 0. 1598min-1, higher than Bi _ 2WO _ 6 (0. 0996 min-1), TiO _ 2 (0.0165 min-1) and P25 (0.0255 min-1). The degradation rate of TB2 catalyst under visible light for 40min and TC was 63. 3%, while pure Bi _ 2WO _ 6 was only 33.9%, and pure TiO _ 2 was only 56. 9%. The prepared compound enhances photocatalytic degradation of RhB, TC and CIP catalytic activity under the irradiation of visible light, and is attributed to the low recombination rate of light generated by the heterogeneous interface between the semiconductors. The fluorescence intensity of TiO _ 2/ Bi _ 2WO _ 6 complexes is lower than that of pure Bi _ 2WO _ 6, which shows that the formation of TiO _ 2/ Bi _ 2WO _ 6 composites inhibits the recombination of electrons and holes. Photochemical photo-current and impedance testing also indicate rapid transfer of photogenic carriers. Electron spin resonance (ESR) shows that the super-oxygen free radical is the main active species, which is consistent with the free radical trapping experiment. Finally, TiO _ 2/ Bi _ (3.64) Mo _ (0.364) Mo _ (0.036) O _ (6.55) composite photocatalyst was prepared by in-situ-solvent thermal method with different TiO _ 2 loading. The photocatalytic activity of Bi _ (3.64) Mo _ (0.364) Mo _ (0.036) O _ (3.64) Mo _ (0.364) Mo _ (0.364) Mo _ (0.036) O _ (6.55) (recorded as TBMO _ 3) was significantly improved when TiO _ 2 was introduced. Photocatalytic degradation of RhoB B solution by photocatalyst is a first-order kinetic reaction. The rate constants of TBMO _ 3 were 0. 2068min-1, respectively, Bi _ (3.64) Mo _ (0.036) O _ (6.55), P25 and TiO _ 2 were 4. 5, 10 and 94 times, respectively. By taking full advantage of the high specific surface area (134,24m2 路 g-1) of TiO _ 2, the specific surface area and porosity of the composite material were investigated. The results show that TBMO _ 3 has a short average life of 4.61 ns and higher photocatalytic activity can be attributed to effective charge transfer and separation compared with Bi _ (3.64) Mo _ (0.036) O _ (6.55) (6.77 ns). The fluorescence spectrum test further proves that the separation and transport of photogenic carriers can be effectively achieved by the synergistic effect of TiO _ 2 and Bi _ (3.64) Mo _ (0.036) O _ (6.55), which may belong to the mechanism of Z-type photoionization. TiO _ 2/ Bi _ (3.64) Mo _ (0.036) O _ (6.55) composites have better stability, which indicates that the composites can provide effective strategies in the application of water purification and environment treatment.
【学位授予单位】：湖北师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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