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RISS 인기검색어
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- 저자 : XIAO XIANGYUN (검색결과 1 건)
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Synthesis Pd-Base Nanoparticles in an Aqueous Phase and Their Catalytic Applications
XIAO XIANGYUN 경희대학교 대학원 2021 국내박사
Abstract Synthesis Pd-Base Nanoparticles in an Aqueous Phase and Their Catalytic Applications By Xiangyun Xiao Doctor of Philosophy in Chemical Engineering Graduate School of Kyung Hee University Advised by Prof. Taekyung Yu As we know that the core-shell structure is the highest catalytic structure from the considerable studies. Pd as a long-term recognized catalyst with various and controllable shape and size are widely used in many kinds of applications. In this thesis, the Pd-base core@shell or core@muti-shell structure with two or three metals were synthesized as the nanocatalysts deeply to investigate the effect of structure and composition on catalytic reaction. Furthermore, the catalysts were prepared in an aqueous phase by continuing seed-mediate growth process or one-top method which has the potential to be industrialized. We synthesized the Pd@Pt with various Pt shells, Pd@RuPt, PdAu with muti-shell nanoparticles. Those nanocrystals were used in the direct synthesis of H2O2 from H2 and O2 (DSHP), methanol oxidation reaction (MOR) and formic acid oxidation reaction (FAOR) reactions. These projects are designed based on green, continuous and industrialization, and work for the high conversion and selective use of clean energy. The all synthesis is based on an aqueous phase by seed-mediate continuation process. Coincidentally, it is found a special ion migration during the synthesis and it has some positive effect on the catalytic 2 reaction which has no relevant theoretical theory to explain its mechanism yet. I will introduce it in the final chapter. In chapter 1, the nanoparticles and nanotechnology, the core-shell structure nanoparticles with bimetallic and trimetallic composition and their synthesis in an aqueous phase were introduced. The Pd-based nanocatalysts and their catalytic applications were presented based on the previous studies. A detailed introduction for hydrogen conversion related reactions including DSHP, MOR and FAOR was given. Based on those backgrounds, it will be better understood for my research. In chapter 2, it showed a new facility directly seed-mediated growth process without washing to fabricate the Pd@Pt with high-index facets concave shell by precisely controlling the amounts of regents. The advantages of the novel synthetic method including simple and continue, high yield product, reagents saving, etc. Those Pd@Pt core-shell nanocatalysts with tailored shells and composition possessing enhanced catalytic activity for FAOR and DSHP. In chapter 3, Pd@Pt core-shell nanocatalysts with partially and fully covered shells for the MOR were investigated. Wherever partially or fully covered shell of Pd@Pt core–shell structure preparation is via a direct seed-mediated growth method. We found the morphology of the Pt shell is controlled by reducing agents. Finally, the MOR catalytic activity of partially and fully shell Pd@Pt under the same Pt/Pd ratio were compared. In chapter 4, a one-top method for the core/shell nanoparticles with multishell synthesis was exhibited. It demonstrated that complex shells could be synthesized by a one-pot method in the presence of PAH. The catalytic activity 3 performance of them toward DSHP was checked. We expect this method to be expanded in other core/shell nanoparticles synthesis. In chapter 5, the Pd@Ru and Pd@RuPt trimetallic catalyst synthesized in an aqueous solution by directly seed-mediated growth method. Interestingly, it is found that a trace of Ru is inserted into the Pd structure. The prepared nanoparticles were used as catalysts for MOR. As a result, the introduction of Ru enhanced the catalytic activity for MOR. In chapter 6, the Ru3+ cation exists in Pd which remarkably enhances the Pd catalytic activity for MOR that was to be found firstly. More interesting thing is that the Ru3+ have the ion migration phenomenon which is like the ion migration in perovskite. We will deeply study this project, like using the in-situ observation and DTF calculation to find the mechanism, and expand the Ru3+ to Fe3+ Cu2+, and so on. In chapter 7, the conclusion of this research and future works of my next plan were described. Finally, my subject provided the opportunities and challenges for further refining the nanostructure of metal‐based catalysts and improving catalytic performance as well as the commercial viability. Key words: Core-shell structure, An aqueous phase synthesis, Catalysts, Hydrogen conversion.
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