| Summary: | 博士 === 國立臺灣大學 === 化學研究所 === 101 === This thesis focuses on the synthesis and fabrication of highly electrocatalytic hybrid nanomaterials (NMs) for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs). The thesis is divided into six parts. Chapter one introduces the background of DMFCs, fundamental understanding of the structure–activity relationship of the electrocatalysts, and various catalysts that are being used in the anodes and cathodes of DMFCs. Chapter two introduces the techniques used for characterization of NMs synthesized in this study. Chapter three deals with the synthesis of Se/Ru core/shell nanoparticles (NPs) for potential use in cathode electrocatalysts. By controlling the concentration of RuCl3, Se/Ru0.2, Se/Ru0.7, and Se/Ru1.1 core/shell NPs were obtained. The mass activities of as-prepared catalysts were 58.0, 32.1, and 12.5 A/g, respectively; part of these values are higher than that (2.2 A/g) of a commercial PtRu electrode and those (22.8, 28.0, and 24.5 A/g) of traditional carbon-supported RuxSey electrodes. The fourth chapter describes about an impregnation method to prepare Se/Ru-Au nanocomposites from 100-nm Se/Ru core-shell NPs and Au NPs (diameters 14, 32, or 56 nm). Au NPs tend to be adsorbed onto Se/Ru core-shell NPs to form Se/Ru-Au nanocomposites. The mass activities of the bimetallic Se/Ru-Au14, Se/Ru-Au32, and Se/Ru-Au56 toward the ORR were found to be 116.3, 73.0, and 87.7 A g-1, respectively, which are much higher than those of traditional RuxSey catalysts. Moreover, Se/Ru-Au14 electrodes are highly active over at least 100 cycles. The fifth chapter describes the synthesis and catalysis of Cu2-xS/carbon nanodots (C dot) electrodes for ORR in DMFCs. The onset potential of the ORR for Cu2-xS/C dot NMs is 0.92 V (vs. Ag/AgCl), revealing a good ORR activity of these NMs. The Cu2-xS/C dot electrodes (mass loading: 2.26 mg cmmg cm-2) provide a mean limiting density of -1.77 mA cm-2 at a scan rate of 5 mV s-1 and rotation rate of 3600 rpm. Compared with Pt/C electrodes, Cu2-xS/C dot electrodes were more tolerant against methanol poisoning. The low-cost, electrochemically stable, and highly active Cu2-xS/C dot electrode has great potential as a cathode catalyst for DMFCs. In the sixth chapter, a facile method has been demonstrated for the preparation of PdCu NPs with various morphologies from Pd2+ and Cu2+ reduced by ascorbate in the presence of dodecyltrimethylammonium chloride at 95 °C. The content of copper atoms not only controls the morphology, but also affects the catalytic activity toward MOR in alkaline media. With advantage of high electrochemical activity, stability, and cost effectiveness, the porous PdCu NPs hold great potential as an anode catalyst for DMFCs.
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