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Pd基纳米催化剂的设计与制备及其对甲酸氧化和氧气还原反应的催化性能
陈东
学位类型博士
导师杨军
2016-07
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业化学工艺
关键词Pd基纳米颗粒 结构调控 电子效应 甲酸氧化反应 氧气还原反应
摘要

由于金属Pd对FAOR和ORR可观的催化活性以及其具有比Pt更低廉的价格,因此,Pd基纳米颗粒的设计与制备已经成为DFAFCs电极反应催化剂研究的热门。纳米颗粒的催化性能很大程度上取决于其的结构,因此,精确地调控纳米颗粒的结构是提升其催化属性的主要手段。本论文通过对Pd基纳米颗粒的结构进行调控,利用所调控出的纳米颗粒的结构优势和颗粒中各组分间的电子效应来提升其对FAOR和ORR的催化性能。本论文具体的研究内容如下:1. 在水溶液中发展出一种既简单又经济的制备空心Pd纳米颗粒(hPd)的方法。对制备过程中出现的颗粒进行了详细的表征,并提出了空心结构的形成机制。利用FAOR验证了hPd纳米颗粒增强的催化性能。另外,为了提高hPd的制备浓度,将此制备方式被拓展到有机相中油胺中,制备出炭载hPd纳米颗粒,通过FAOR和酸性溶液中ORR考察了所制备催化剂的催化性能。2. 基于油胺中hPd纳米颗粒的制备,发展出半导体Ag2S与hPd复合结构纳米材料(Ag2S-hPd)的制备方式。通过TEM表征手段,观察到了这种纳米复合材料的形成过程,进而提出了其的制备机制。利用XPS手段表征了半导体Ag2S与Pd之间的电子耦合效应,并通过FAOR考察了电子耦合效应对复合材料中Pd纳米颗粒催化性能的影响。3. 利用Ag-Pd合金去合金过程对Pd造成的额外晶格应变,发展了一种制备具有更大晶格应变效应的核壳型Au@Pd纳米颗粒。通过XPS表征技术揭示了这种更大程度的晶格应变效应。通过对比采用种子生长法直接得到的Au@Pd纳米颗粒催化ORR性能,探究这种更大程度的晶格应变效应对催化性能的影响。4. 另外,发展了一种利用Au催化制备亚纳米壳核壳型Au@Pd纳米颗粒的方法。通过高分辨率STEM技术,详细地表征了核壳型Au@Pd纳米颗粒壳层的Pd原子层数,并通过相关的验证实验得出了Au催化核壳型Au@Pd纳米颗粒的形成机制。另外,通过酸性溶液中的ORR,验证了Pd壳中的晶格应变效应对其催化性能的提升。5. 通过对纳米颗粒的几何结构进行裁剪,制备出了铃铛型(CBS)Pt-Pd纳米颗粒。通过TEM,HRTEM对所制备的铃铛结构进行了确认,并考察了CBS Pt-Pd催化ORR的活性及在甲醇存在下对ORR的选择性。6. 发展了一种通过Cu纳米颗粒与Pd2+前驱体间的GRR制备树枝状Cu-Pd合金纳米颗粒的方式。对树枝结构及其成分进行了详细的表征,并探究了树枝状的Cu-Pd合金纳米颗粒在FAOR中催化性能提升的原因。

其他摘要

Owing to good catalytic performance of metal palladium on formic acid oxidation reaction (FAOR) and oxygen reduction reaction (ORR) as well as the relatively low-cost than that of Pt, the design and preparation of Pd-based nanoparticles have been a hot orientation of research on electrode catalysts of direct formic acid fuel cells (DFAFCs). It is well known that the catalytic performance of a catalyst strongly depend on its structure, hence, precisely tailoring the structure of catalysts have become one of the main ways for the improvement of catalytic properties. In this thesis, we concentrated on tailoring the structure of Pd-based nanoparticles by wet-chemistry method, and making use of their structural advantage and the formed electronic effect to enhance their catalytic performance for FAOR and ORR. The detail achievements are listed as following:1. A facile and economy way for the preparation of hollow Pd (hPd) nanoparticles has been developed in aqueous solution. The nanoparticles in the process of the preparation of hollow structure were characterized in details, and the formed mechanism of hPd nanoparticles was proposed. The enhanced catalytic properties of hPd nanoparticles for FAOR were verified. In addition, in order to increase the prepared concentration of hPd nanoparticles, their prepared way in aqueous solution was modified, and the prepared method of carbon loaded hPd nanoparticles were developed in oleylamine, whose catalytic properties for FAOR and ORR in acid mediate were also measured.2. The heterogeneous nanocomposites consisting of silver sulfide and hollow structured Pd nanoparticles (Ag2S-hPd) were prepared on the basis of the preparation of hPd nanoparticles in oleylamine. The heterogeneous structure of Ag2S-hPd was characterized by TEM, and the electronic couple effect between Ag2S and Pd was confirmed by XPS technique. The influence of electronic couple effect on the catalytic properties of Pd nanoparticles in Ag2S-hPd were investigated by means of FAOR.3. Because the process of the delloy would lead to extra lattice strain, the core-shell Au@Pd nanoparticles with larger lattice strain effect have been prepared. The larger lattice strain effect were uncovered by XPS technique, whose influence on the catalytic properties towards ORR in acid mediate was investigated, compared with the catalytic behavior of core-shell Au@Pd nanoparticles via seeded- mediated growth for ORR. 4. The gold-catalyzed strategy for the synthesis of core-shell Au@Pd nanoparticles with subnanometer-thick palladium shells has been developed. The atomic layers in subnanometer-thick palladium shells were gained using high resolution STEM technique, and the formed mechanism of core-shell Au@Pd nanoparticles via Au core catalysis was also proposed, based on the results of the related verification experiments. In addition, it was verified that the lattice strain effect in core-shell Au@Pd nanoparticles improved their catalytic properties for ORR.5. Cage-bell (CBS) Pt-Pd nanoparticles were prepared by tailoring the geometric structure of nanoparticles. The CBS structure was clearly confirmed by TEM and STEM technique. The catalytic properties of CBS Pt-Pd nanoparticles and their selectivity for ORR were measured.6. The way for the preparation of dendritic Cu-Pd alloy nanoparticles have been developed via GRR between Cu nanoparticles pre-prepared and Pd2+ precursor. The morphology and composition of dendritic structure were characterized in detail, and the reason that the dendritic Cu-Pd alloy nanoparticles highly efficiently catalyzed FAOR was investigated. 

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/22880
专题研究所(批量导入)
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陈东. Pd基纳米催化剂的设计与制备及其对甲酸氧化和氧气还原反应的催化性能[D]. 北京. 中国科学院研究生院,2016.
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