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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
URI标识: http://ir.rcees.ac.cn/handle/311016/36960
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Recommended Citation:
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.
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