| Summary: | 博士 === 國立交通大學 === 工學院加速器光源科技與應用碩士學位學程 === 105 === Given extreme global climate and gradual shortage of natural resources, efficiently using current energy sources and seeking sustainable and renewable energy are the primary objectives of all countries worldwide. A new energy material that has efficient energy conversion/generation/storage is urgently demanded. In many of these important energy material systems, the change in atomic and electronic structure upon reaction provide the fundamental understanding of the physical and chemical properties of an energy material. Synchrotron based-X-ray spectroscopy is very powerful tool to investigate the atomic and electronic structures of a matter. Emerging in situ techniques allow one to look into above properties under working conditions. This thesis focuses on the atomic and electronic structures of several energy materials by using (in situ) X-ray spectroscopic techniques. The thesis is cataloged into three parts. In the first part, pristine and Mo-modified V2O5 smart thin films were prepared by the sol–gel spin coating method. In situ X-ray absorption spectroscopic (XAS) results indicate that upon gasochromic (electrochromic) coloration, adsorption of hydrogen (lithium) adds electrons to the V 3d t2g orbital, lowering the charge state of vanadium. Structural modulation is essential for the gasochromic/electrochromic reaction. The Mo-modified V2O5 film exhibits faster coloration owing to the apical V–O bond differs from that in the pristine V2O5 film. Second part of the thesis reports the different functionalized carbon nanotubes (CNT) were decorated with MnO2 nanoflakes as supercapacitors by a spontaneous redox reaction. The different morphologies of nanoflaky MnO¬2 were formed owing to different functional groups created at the surface of carbon nanotubes, leading to different capacitive behaviors. In situ X-ray absorption reveals that the C 2p π* state of CNT and the tunnel size of MnO2 in pseudo-capacitor materials are critical for the capacitive performance. Finally, the water splitting mechanism of ZnO/Fe2O3 core-shell nanowires was investigated by (in situ) XAS and scanning transmission X-ray microscopy. Analytic results demonstrated that the Fe2O3/ZnO core-shell NW exhibits strong anisotropic effects and thus provides higher electron transport ability. In situ XAS demonstrated that holes (electrons) of ZnO (Fe2O3) are transferred from Zn 4p (Fe 3d) to Fe 3d (Zn 4p) state under photoelectrochemical condition.
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