The Design And Preparation Of Pd-Based Nanocatalysts And Their Catalytic Properties On Formic Acid Oxidation Reaction And Oxygen Reduction Reaction

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.