| 题名 | AuPd电极材料制备及三维电催化氧化难降解有机物的研究 |
| 作者 | 覃英华 |
| 学位类别 | 硕士 |
| 答辩日期 | 2016-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 曲久辉 |
| 关键词 | AuPd合金，三维电催化，离子液体，双酚 A AuPd alloy, three-dimensional electrocatalysis, ionic liquids, BPA |
| 其他题名 | The synthesis of AuPd electrode materials and their application in three-dimensional electrocatalytic oxidation of refractory organics |
| 学位专业 | 环境工程 |
| 中文摘要 | 传统二维电催化技术的效率受限于其传质速率，三维电极的引入有效的解决了这一难题。三维电极材料是三维电催化技术的关键，对三维电催化技术的效率和稳定性起决定作用。近年来，催化剂负载型非均相三维电极材料的开发成为研究热点，其中 Au、Pd等贵金属由于其突出的非均相电催化性能而被用作三维电极材料的催化剂。但其原位产生的 H2O2氧化能力有限，而且在催化剂使用过程中贵金属易流失，因而其催化体系的氧化能力和循环稳定性仍待提升。针对以上问题，本文开发出新型高效、稳定的负载型非均相三维电极材料 AuPd/Fe3O4和AuPd/Carbon，构建了三维电催化体系，并考察了其对两类典型难降解有毒有机污染物的处理效果、转化规律、作用机理及体系稳定性等。 1）通过共沉积方法合成 AuPd/Fe3O4复合材料，采用XRD、SEM、XPS等表征手段，确定Au，Pd以合金形式负载在呈正八面体的Fe3O4基底上。以AuPd/Fe3O4作为粒子电极构建三维电催化体系，考察其对典型离子液体1-丁基-3-甲基咪唑（BMIM）六氟磷酸盐的降解性能，结果表明该体系可实现对BMIM的高效降解，其降解规律遵循阳极芬顿氧化（AFT）模型。该体系中，AuPd催化剂利用电解产生的 H2和 O2反应生成 H2O2，而载体 Fe3O4则通过释放Fe2+催化H2O2产生HO•。BMIM在HO•的作用下主要生成1-butyl-3-methyl-2,4,5-trioxoimidazolidine,1-butyl-3-methylurea及N-butyl-formamide三种中间产物，随后逐步分解成为小分子有机酸或直接矿化。Fe3O4载体不仅调控了体系中的氧化物种，且使粒子电极具备磁分离性能，便于回收和循环利用，使得 AuPd/Fe3O4三维电催化体系具有较好的循环稳定性，经过 7次循环使用后仍然能保持 90%以上的降解性能。 2）为了克服 AuPd/Fe3O4复合材料在使用过程中贵金属流失导致的循环稳定性较差的问题，构建了碳纤维负载 AuPd合金的 AuPd/Carbon三维固定式电极，考察其对典型环境内分泌干扰物双酚A（BPA）的降解特性。研究表明，基于AuPd/Carbon和感应铁电极构建的三维电催化体系能够高效去除BPA。该体系中AuPd催化剂原位产生H2O2，感应铁电极提供 Fe2+并催化 H2O2生成 HO•，实现对 BPA的高效去除。BPA在该体系中的降解途径主要为酚羟基邻位羟基化和连接两个苯环的C-C键断裂两种途径，主要产生 5-Hydroxybisphenol，4-Isopropylphenol，4-(2-hydroyprpyl)-2-hydroxyphenol三种中间产物，最后被直接矿化或生成小分子有机酸。与 AuPd/Fe3O4三维电催化体系相比，AuPd/Carbon三维电催化体系具有更好的循环稳定性，循环使用 20次后仍保持 100%的降解性能。对 AuPd/Carbon进行 SEM、XRD及 XPS分析表征发现，使用后的 AuPd/Carbon基本保持原有的形貌、晶型以及元素组成和价态，有效解决了 AuPd/Fe3O4复合材料贵金属流失的问题，可实现 AuPd的三维电催化材料的高效重复利用，为三维电催化技术在有机废水处理中的应用提供了依据。 |
| 英文摘要 | The efficiency of the traditional two-dimensional electrocatalytic technology is limited by the mass transfer rate, while the introduction of three-dimensional (3D) electrodes effectively solved this problem. The 3D electrode material is the key to the 3D electrocatalytic technology and possesses crucial importance to the electrocatalytic efficiency and recycle ability. In recent years, the development of catalyst-supported heterogeneous 3D electrode materials has been a research focus, notable metals like Au, Pd have been used as the catalyst of 3D electrode materials for the outstanding heterogeneous catalytic properties such as the in-situ generation of H2O2, while the oxidation ability of H2O2 is still limited and precious metals are easy to lose in the using process, therefore it is also necessary to improve the oxidation ability and recycle ability of the electrocatalytic system based on Au and Pd. Aimed at solving the problems mentioned above, in this research, new type of highly efficient and stable catalyst-supported 3D electrode materials AuPd/Fe3O4 and AuPd/Carbon were developed based on AuPd alloy, and used for the establishment of 3D electrocatalytic system for the degradation of two typical refractory organic pollutants, the removal efficiency, degradation rule, reaction mechanism and recycle ability were investigated. 1) AuPd/Fe3O4 composite material was synthesized through a deposition method and it was confirmed by the characterization method of XRD, SEM and XPS that AuPd alloys were loaded on the octahedral Fe3O4 substrates. The 3D electrocatalytic system based on AuPd/Fe3O4 particle electrodes was established for the degradation of 1-butyl-3-methylimidazolium (BMIM) hexafluorophosphate, and exhibited great removal efficiency for BMIM and the degradation rule followed the Anodic Fenton Treatment (AFT) model. In this system, H2O2 was generated by the AuPd catalyst by using the H2 and O2 produced in electrolysis, and Fe2+ was released from the Fe3O4 substrate, thus HO• was generated, which contributed to the degradation of BMIM into three main intermediates including 1-butyl-3-methyl-2,4,5-trioxoimidazolidine, 1-butyl-3-methylurea and N-butyl-formamide and finally into small organic acids or directly carbonized into CO2 and H2O. Fe3O4 substrates not only changed the oxidative species in the system , and also made the particle electrodes magnetically recyclable and easy to reuse, therefore the AuPd/Fe3O4 3D electrocatalytic system demonstrated preferable recycle stability and remained a removal efficiency above 90% after using for 7 times. 2) In order to avoid the waste and loss of noble metals caused by the unsatisfactory recycle ability, further research on the synthesis of AuPd/Carbon composite fixed electrode and the application in the 3D electrocatalytic degradation of typical environmental endocrine disruptors bisphenol A (BPA) was carried out. It turned out that the AuPd/Carbon-based 3D electrocatalytic system exhibited excellent performance for the removal of BPA. In this system, HO• was generated from the reaction of H2O2 produced by AuPd alloys and Fe2+ provided from the induction iron electrode, thus BPA was efficiently degraded. The degradation paths of BPA mainly included the fission of the C-C bond which linked the two benzene ring, and the hydroxylation of benzene hydroxyl ortho,with the generation of 5-Hydroxybisphenol，4-Isopropylphenol，4-(2-hydroyprpyl)-2-hydroxyphenol as main intermediates, finally most BPA was mineralized and a small part of BPA was broken down into small organic acids. The AuPd/Carbon-based 3D electrocatalytic system exhibited much better recycle ability compared with the AuPd/Fe3O4-based 3D electrocatalytic system, with a result that BPA could still be totally removed in 60 min after the same AuPd/Carbon fixed electrode had been used for twenty cycles. The characterization by SEM, XRD and XPS indicated that AuPd/Carbon after use almost remained the morphology, crystal form and the elemental composition and valence state, demonstrating that the effective solution to the problem of the loss of noble metal during the process, which provided a guarantee for the high efficiently reutilization of the AuPd-based 3D electrocatalytic system and a basis for application of 3D electrocatalytic technologies in the treatment of organic wastewaters. |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/36960]  |
| 专题 | 生态环境研究中心_环境水质学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 覃英华. AuPd电极材料制备及三维电催化氧化难降解有机物的研究[D]. 北京. 中国科学院研究生院. 2016. |
| 个性服务 |
| 查看访问统计 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
修改评论