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Research paper : Basic materials research for the development of ubiquitous-energy devices (M. Kohyama et al.)−49−Synthesiology - English edition Vol.2 No.1 (2009) in bulk is activated by being surrounded by the layered Mn-rich domain that is advantageous for diffusion of Li ions, and then when Li becomes depleted in the Fe-rich domain, the Li ions are extracted even from the Mn-rich domain. It is thought that oxygen provides charge compensation in Li extraction from the Li2MnO3 domain composed of tetravalent Mn. Decrease of capacity is thought to occur due to the desorption of neutral oxygen by charge compensation, and the actual reduction in oxygen concentration was observed in the STEM-EELS spectrum imaging.It was possible to clarify the mechanism of increased capacity where the chemical nano-domain structure activated each component material, by discovering the chemical nano-domain structure utilizing the TEM technology and by developing the visualization technology for quantitative distribution of Li-ion concentration. It is greatly significant to clarify the specific involvement of the nanostructure in the performance of positive electrode materials. Currently, material performance is being improved from the perspective of optimal control of such chemical nano-domain structure. The essential factor that enabled the above results was the research conducted through daily communication of issues, topics, and experimental observation plan through close collaboration with the Li2MnO3-LiFeO2 development group.4.2 Microscopic structure and deterioration mechanism of electrode catalysts in fuel cellsIn a polymer-electrolyte fuel cell, electrons are extracted by the dissociation and oxidation of a fuel hydrogen molecule at the Pt particle of the negative electrode (H2 2H+ + 2e−) by using the structure in which Pt particles are supported by carbon material (Pt/C electrode) as electrode catalysts, and proton H+ transfers to the positive electrode through the polymer electrolyte. Similarly, water is produced by reaction of proton and oxygen on the Pt particle at the positive electrode (1/2O2 + 2H+ + 2e− H2O). At this moment, electrons from the negative electrode are used through the carbon and the conductor. Since CO often mixed in the hydrogen gas suppresses the catalytic activity of Pt particles at the negative electrode (CO poisoning), Pt-Ru alloy particles are used. It is important to increase the reaction efficiency while reducing the amount of rare metal Pt by controlling the electrode composition as well as the size and dispersion of Pt particles and Pt alloy particles.Deterioration through use is an issue for the Pt/C electrode, and the clarification of that mechanism is demanded. Under close collaboration with the group conducting the development of electrode catalysts and deterioration testing, we attempted clarification through TEM observation[11]-[13]. The TEM observation of the electrode catalysts of fuel cells was extremely rare. Electrolyte-electrode catalyst assembly was sliced using ultra-microtome to prepare the TEM samples, and optimal observation conditions were sought by trial and error. Figure 5 shows the typical high-resolution transmission electron microscope (HRTEM) image of the PtRu/C electrode catalysts. The lattice image of the fine particles of the catalyst could be seen clearly, indicating that excellent high-resolution observation was possible.Fig. 5 High-resolution TEM image of PtRu/C electrode catalysts.Fig. 6 TEM images of the precipitation and growth of Pt particles inside the electrolyte film, caused by Pt dissolution from the Pt/C positive electrode in various testing conditions.(a) Nitrogen was supplied to the Pt/C electrode with an electrolyte film of thickness 50 µm, under the potential for 87 h. (b) Nitrogen was supplied to the electrode with an electrolyte film of thickness 175 µm, under the potential for 87 h. (c) Air was supplied to the electrode with an electrolyte film of thickness 175 µm, under the potential for 30 h. (d) Air was supplied to the electrode with an electrolyte film of thickness 175 µm, under the potential for 87 h. The features of the precipitation and growth of Pt particles depend on the thickness of the electrolyte film, supplied gasses, and the time of potential charge.Fig. 7 First-principles calculation of a Pt10 cluster/graphene system. Valence-electron charge distribution of the relaxed configuration indicates little electron transfer or orbital hybridization at the interface.CCCCCCCPtPtPtPtPt

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