【作者】 李红；

【导师】 李新勇；

【作者基本信息】 大连理工大学 ， 环境科学， 2013， 博士

【摘要】 目前对空气中挥发性有机污染物(VOCs)的治理是环境领域的重要问题。最常见、最典型的VOCs是甲苯,基于太阳能利用的光催化技术在控制甲苯等VOCs方面表现出十分重要的应用前景。因此开发基于太阳能利用的高量子效率的光催化体系已成为一项重要的研究课题。本研究以纺锤状α-Fe2CO3为基材料构建α-Fe2O3/GO、Ag/a-Fe2O3及g-C3N4/a-Fe2O3等复合体系,利用原位红外光谱技术,研究甲苯在这些材料上的可见光催化降解过程,探讨复合光催化体系内异质界面上光生电荷的迁移机制和光催化降解机理。研究成果如下：(1)合成出空心纺锤形貌的α-Fe2O3催化剂,样品纯度高、结晶好。通过对样品进行DRS、BET表征以及光电响应机理分析,发现其空心结构增强了样品的可见光吸收能力和表面吸附能力,且样品具有一定的光生电荷分离能力。(2)通过浸渍和光照还原法制备了贵金属银负载的Ag/α-Fe2O3复合体系。利用原位红外光谱技术考察了可见光下复合催化剂对甲苯的光催化活性,以及不同Ag负载量对Ag/α-Fe2O3降解率的影响。结果发现在6h的氙灯照射下,该复合体系对甲苯光催化活性,明显高于商用α-Fe2O3和空心纺锤状α-Fe2O3,并且对甲苯的降解完全,降解产物为C02和水。Ag在α-Fe2O3上的表面等离子共振效应提高了光生电荷的分离效率。结果还发现Ag的负载量对Ag/α-Fe2O3复合体系的降解率也有一定程度的影响,当Ag负载量为1.0wt%左右时,Ag/α-Fe2O3的降解率最高,达到88%。(3)制备出α-Fe2O3与新型碳材料石墨烯的复合体系α-Fe2O3/GO,该复合体系比单一空心纺锤状α-Fe2O3具有更强的可见光吸收能力、光生载流子的分离能力和表面的吸附能力。该催化剂对甲苯进行可见光催化降解,6h的降解率为80%。利用原位红外光谱技术检测出反应产物为苯甲醛、苯甲酸、C02和水。降解率的提高主要归因于石墨烯优越的吸附特性以及GO的加入引起了复合体系导带电位的负向移动,从而加快了光生载流子的有效分离,提高了量子效率。(4)通过简单溶剂热法成功地将α-Fe2O3纳米颗粒负载在g-C3N4上形成了光催化复合体系g-C3N4/α-Fe2O3该复合体系对甲苯进行可见光催化降解,降解产物为苯甲醛、苯甲酸、CO2和水,6h后甲苯的降解率为91%。其高的光催化性能主要归因于复合结构中α-Fe2O3和g-C3N4的协同效应以及大的比表面积,同时,复合体系中各组分的质量比也影响其光催化活性,结果显示,当组分中g-C3N4含量为70wt%时g-C3N4/α-Fe2O3复合体系光催化活性最高并且具有一定的稳定性,在多次重复使用后其催化活性基本保持不变。(5)对比发现上述α-Fe2O3基复合体系对甲苯的可见光催化降解活性顺序为：g-C3N4/α-Fe2O3复合体系>Ag/α-Fe2O3复合体系>α-Fe2O3/GO复合体系>纺锤状空心α-Fe2O3。更多还原

【Abstract】 Currently with increasing environmental pollution, the management of volatile organic compounds (VOCs) in the air is a top priority. A most common and typical example of VOCs is toluene. Photocatalytic technology based on the utilization of solar energy has demonstrated a very important prospect in the application of controlling toluene and other VOCs. So the development of photocatalytic system with high quantum efficiency based on solar energy utilization has become an important research topic. On this basis, α-Fe2O3was used as a base material to construct α-Fe2O3/GO, Ag/α-Fe2O3and g-C3N4/α-Fe2O3complex systems. In situ infrared spectroscopy was applied to study the photocatalytic degradation process of toluene over these materials under visible light. Light-induced charge migration and photocatalytic degradation mechanisms were explored in the constructed photocatalytic systems. The main results obtained are as follows:(1) Successful synthesis of the hollow spindle-shaped α-Fe2O3catalyst of high purity as well as good crystallinity. Through the DRS, BET characterization on the samples and detailed analysis of SPV mechanisms, enhanced visible-light absorptive capacity and adsorption capacity as well as effective separation capability of photogenerated carriers were found due to the hollow structure of the sample.(2) Ag/α-Fe2O3composite systems were prepared by impregnation of loading precious metal silver. Photocatalytic activity and the effects of different Ag loadings on toluene degradation rates over Ag/α-Fe2O3under visible light were investigated using in situ infrared spectroscopy. The results showed that during the xenon lamp irradiation for6h, the photocatalytic activity of toluene over this complex was higher than that over commercial α-Fe2O3and hollow spindle-shaped α-Fe2O3. Furthermore, complete degradation of toluene into degradation products of CO2and water could be achieved and the degradation rate reached88%over this composite. The enhanced photocatalytic activity after loading Ag catalyst was mainly attributed to Ag and α-Fe203composite system improves the light-induced charge separation efficiency. We also found that Ag loadings had some influence on the degradation rate by Ag/α-Fe2O3to a certain extent. When Ag loading was about1.0wt%, Ag/α-Fe2O3had a highest degradation rate of88%.(3) Preparation of a composite system of α-Fe2O3and graphene based new carbon material α-Fe2O3/GO. The complex system has a stronger ability than a single α-Fe2O3in absorbing visible light, enhanced photo-induced carriers separation and stronger surface adsorption capabilities. The photocatalytic toluene degradation rate of80%could be achieved in6h using the composite catalyst compared with a single α-Fe2O3. By using in situ infrared spectroscopy for the detection of the reaction products, benzaldehyde, benzoic acid, CO2and water were identified. Increased degradation rate was mainly due to the superior adsorption characteristics of graphene, and the introduction of GO caused a shift of the conduction band of α-Fe2O3in the composite system towards the negative direction, thereby speeding up the effective separation of photo-generated carriers and improving the quantum efficiency.(4) Using a simple solvothermal method, we successfully loaded the α-Fe2O3nanoparticles onto g-C3N4to form a composite photocatalytic system g-C3N4/α-Fe2O3. The products over the composite system during the photocatalytic degradation of toluene were benzaldehyde, benzoic acid, CO2and water. The toluene degradation rate of91%in6h. Its high photocatalytic performance is mainly due to the synergistic effect between α-Fe2O3and g-C3N4and a large specific surface area of the complex structure. Meanwhile, the mass ratio of the components in the composite system also affect the photocatalytic activity. The results showed when the component g-C3N4content was70wt%, g-CjN4/a-Fe2O3composite system exhibited a highest photocatalytic activity and had a certain stability since the catalytic activity remained unchanged after repeated use for times.(5) By comoparison, the performance order of α-Fe2O3based composite materials for the photocatalytic degradation of toluene under visible light is g-C3N4/a-Fe2O3composite> Ag/a-Fe2O3composite> a-Fe2O3/GO composite>hollow spindle-shaped α-Fe2O3.更多还原