En esta tesis se estudian la electrocatálisis de algunas reacciones involucradas en las pilas de combustible. Se utilizan electrodos monocristalinos de oro y platino para analizar, a nivel fundamental, los procesos que tienen lugar en la interfase entre electrodo y la disolución. En una primera parte se analiza la oxidación de ácido fórmico e hidracina que son dos combustibles empleados en las celdas de combustible. Posteriormente se estudian reacciones secundarias a las mismas como es la oxidación de CO o la oxidación y reducción de peróxido de hidrógeno.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22780号 / 工博第4779号 / 新制||工||1747(附属図書館) / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 田中 勝久, 教授 陰山 洋, 教授 藤田 晃司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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In dieser Arbeit wurde die Kupferoxidebene des Hochtemperatur - Supraleiters Yttrium- Barium-Kupferoxid (YBa2Cu3O6+y) mit Hilfe von Kernmagnetischer-Resonanz (NMR - nucleus magnetic resonance) unter Drücken von bis zu 4.4GPa untersucht. Es wurden 2 dieser Druckzellen gebaut, sie enthielten verschieden stark dotierte Einkristalle. Die Änderungen der Ladungsverteilungen in der Kupferoxidebene abhängig von der Dotierung und vom Druck lagen hierbei im Fokus der Untersuchungen. Motivation dieser Arbeit war es YBa2Cu3O6+y Einkristalle bei höheren Drücken als zuvor mit NMR zu untersuchen. Dabei wurde der alte Rekord von 1.8GPa (Steven Reichardt 2018) auf 4.4GPa erhöht (aktuelle Arbeit). Da sich die Probenkammer in einer Druckzelle stark verformt, muss die Unversehrtheit der Kristalle an jedem Druckpunkt überprüft werden. Dies wurde unter anderem mit Bildern,welche mit dem Mikroskop durch die transparenten Anvils gemacht wurden, überprüft, als auch durch aufwendige Höhenmessungen der Probenkammer mit speziellen Mikroskopen in Verbindung mit einem Piezo-gesteuertem Probentisch. Durch die exakte Vermessung und Positionierung der Einkristalle auf dem Anvil konnte in Verbindung mit den Höhen- und Druchmessermessungen sichergestellt werden, dass sich der Kristall unter hydrostatischen Druckbedingungen befindet und nicht linear entlang der Zellenachse komprimiert wird, was zu einem Brechen oder einer Veränderung der Orientierung hätte führen können. Eine allgemeine Erkenntnis konnte dabei gewonnen werden, über die Stabilität, insbesondere der Höhe der Probenkammer, welche zunimmt mit dem Durchmesser des Culets. Dies ist entgegen des allgemeinen Prinzipes der Miniaturisierung zum erreichen höherer Drücke, für die Planung der Zellenarchitektur für Einkristallmessungen in NMR-Anvilzellen aber wichtig. Weiterhin mussten auch andere wichtige Parameter für NMR Messungen erfüllt werden. Die Architektur der Mikrospule welche in der Probenkammer um den Kristall gelegt wurde, mussten um den Füllfaktor zu maximieren an die Dimensionen der Kristalls angepasst werden. Dazu wurde eine Methode entwickelt um elliptische Mikrospulen von Hand zu wickeln, darin wurden die flachen Kristalle aufrecht platziert. Damit konnte das Signal auf eine annehmbare Intensität gebracht werden um in endlicher Zeit Messungen realisieren zu können. Mit den Messungen an Yttrium-Barium-Kupferoxid Einkristallen unter Druck konnte gezeigt werden, dass mit steigendem Druck sowohl die zunehmende Dotierung der Kupferoxidebene die Position am Sauerstoffatom bevorzugt, als auch eine Ladungsumverteilung in der Kupferoxidebene induziert wird. Weiterhin wurden NMR-Messungen am Indium Kern des Thermoelektrika Silber-Indium-Tellurid unter Druck durchgeführt. 5 verschiedenen Druckzellen wurden gebaut und bei Drücken bis zu 10GPa wurde gemessen. Bis 2.5GPa konnten Spektren aufgezeichnet werden die einen Anstieg des elektrischen Feldgradienten nahelegten. Dieser anstiegt konnte mit Nutationsexperimenten bestätigt werden. Die Echo-Experimente bei 4GPa und 5GPa wiesen einen starken Signalverlust auf und legten eine Quadropolaufspaltung des Zentralübergangs zweiter Ordnung nahe. Über 5GPa wurde kein Signal mehr gefunden. Nach dem Ablassen des Drucks zurück zu Umgebungsbedingungen wurde wieder ein Signal bei der ursprünglichen Frequenz gemessen.:0 Introduction 1 Theoretical Basics, Page 5 1.1 Nuclear Magnetic Resonance (NMR), Page 6 1.2 NMR Setup, Page 14 1.3 Pressure as Parameter, Page 17 1.4 NMR under Pressure, Page 28 2 Samples, Page 31 2.1 Yttrium-Barium-Copper-Oxide, Page 32 2.2 Silver-Indium-Telluride, Page 42 3 Experimental, Page 45 3.1 Spectrometer and Magnet, Page 46 3.2 Evaluation of the Measured Signals,Page 46 3.3 Micro Electronics, Page 47 3.4 Summary of the Chapter, Page 53 4 Sample Chamber Monitoring for single crystal NMR in high pressure cells, Page 55 4.1 Necessity of Sample Chamber Monitoring, Page 56 4.2 Measurements, Page 57 4.3 error consideration, Page 64 4.4 Discussion, Page 65 5 Single Crystal NMR of YBa2Cu3O6+y up to 4.4 GPa, Page 67 5.1 Doping Level and the Critical Temperature, Page 68 5.2 Orientation of the Single Crystal, Page 73 5.3 Discussion, Page 81 6 Silver-Indium-Telluride NMR under pressure, Page 83 6.1 Introduction, Page 84 6.2 Sample, Page 85 6.3 Pressures Cells, Page 85 6.4 Measurments, Page 87 6.5 Discussion, Page 97 7 Summary and Outlook, Page 99 7.1 Summary, Page 100 7.2 Conclusion and Outlook, Page 103 Appendix A Appendix, Page 107 A.1 Spectra, Page 108 Y-6.85 Cell, Page 108 Y-6.5 Cell, Page 113 References 127 / In this work the CuO2-plane of the high temperature superconductor yttrium-bariumcopper-oxide (YBa2Cu3O6+y) is investigated by nuclear magnetic resonance (NMR) under pressures up to 4.4GPa. Two high pressure NMR cells were built and filled with differently doped single crystals. The changes of the charge distribution in the CuO2-plane depending on doping and depending on pressure were the focus of the investigations. The motivation of this work was to extend the NMR measurements of YBa2Cu3O6+y single crystals in NMR anvil cells with pressures not achieved before. The old record (from Steven Reichardt 2018) of YBa2Cu3O6+y single crystals up to 1.8GPa was increased to 4.4GPa with this work. Due to the large deformation of the sample chamber, the integrity of a single crystal has to be checked at every pressure point. This was done by pictures, shot through the transparent anvils as well as height measurements of the sample chamber with a special microscope combined with a piezo controlled table. The exact measurements of the position of the single crystals as well as the height and diameter measurements assured that the single crystal is still in hydrostatic conditions or if it is tilted or pressurized linearly. A general cognizance about the stability of the sample chamber was acquired, especially about the stability of the height, which increases with the diameter of the culet. This is contrary to the general principle of miniaturization to reach higher pressures, if single crystals are of interest. The aim here is to have a stable sample chamber for good measuring conditions for NMR under pressure. Further, other expectations for the parameters of a NMR experiment had to be fulfilled as well. The architecture of a microcoil, which is placed around the crystal in the chamber, had to match the flat crystal shape to increase the filling factor and with this the signal to noise ratio (SNR) of the probe. For this, a method to wind elliptical micro coils by hand under the microscope was developed. Thereby signal intensity could be increased to an acceptable value which allowed more rapid measurements. With the measurements on YBa2Cu3O6+y single crystals under pressure it was shown that increasing pressure increase the hole doping in the CuO2-plane. Furthermore a redistibution of the charges in the CuO2-plane occurs. In a second part of this thesis 115In NMR measurements on the thermoelectric AgInTe2 under pressure up to 10GPa in 5 different cells were preformed. Up to 2.5GPa spectra were recorded which could be explained by an increase of the quadrupole frequency. This increase was verified by a power dependent nutation spectroscopy experiment. The echo experiments of pressures between 3GPa and 5GPa showed a high signal loss and pointed to an increasing disorder and a second order affected central transition of a powder spectrum. No signal was found above 5GPa despite elaborate searches in particular for a possible metallic component. After the pressure release a signal was found again at ambient conditions frequency.:0 Introduction 1 Theoretical Basics, Page 5 1.1 Nuclear Magnetic Resonance (NMR), Page 6 1.2 NMR Setup, Page 14 1.3 Pressure as Parameter, Page 17 1.4 NMR under Pressure, Page 28 2 Samples, Page 31 2.1 Yttrium-Barium-Copper-Oxide, Page 32 2.2 Silver-Indium-Telluride, Page 42 3 Experimental, Page 45 3.1 Spectrometer and Magnet, Page 46 3.2 Evaluation of the Measured Signals,Page 46 3.3 Micro Electronics, Page 47 3.4 Summary of the Chapter, Page 53 4 Sample Chamber Monitoring for single crystal NMR in high pressure cells, Page 55 4.1 Necessity of Sample Chamber Monitoring, Page 56 4.2 Measurements, Page 57 4.3 error consideration, Page 64 4.4 Discussion, Page 65 5 Single Crystal NMR of YBa2Cu3O6+y up to 4.4 GPa, Page 67 5.1 Doping Level and the Critical Temperature, Page 68 5.2 Orientation of the Single Crystal, Page 73 5.3 Discussion, Page 81 6 Silver-Indium-Telluride NMR under pressure, Page 83 6.1 Introduction, Page 84 6.2 Sample, Page 85 6.3 Pressures Cells, Page 85 6.4 Measurments, Page 87 6.5 Discussion, Page 97 7 Summary and Outlook, Page 99 7.1 Summary, Page 100 7.2 Conclusion and Outlook, Page 103 Appendix A Appendix, Page 107 A.1 Spectra, Page 108 Y-6.85 Cell, Page 108 Y-6.5 Cell, Page 113 References 127

The crystal structures of (NH4)2TeBr6 and Ce2TeBr6 have been reinvestigated using X-ray diffraction from powders and single crystals. Three dimensional single crystal intensity data obtained photographically have been used to refine these structures, which are of the cubic K2PtCl6 type, by a full matrix least squares analysis. The Te-Br bond is found to be 2.70* in both crystals after correction for the thermal notion of the atoms. A phase transition in (NH4)2TeBr6 has been observed at about 183°K. Pros an examination of Weissenberg photographs taken at 163°K, the low temperature phase is found to be tetragonal, space group p4/mnc (D64h) with a « 7.501+/-0.005* and c =10.765*+/-0.005*. The transformation in this case is probably similar to that reported in other isomorphous crystals, e.g., K2snBr6. A review of other crystals with similar structure is included in this thesis and the theory of X-ray diffraction as applicable to the present problem is discussed briefly. / Thesis / Master of Science (MSc)

Of the emerging photovoltaic technologies, perovskite solar cells (PSCs) are arguably among the most promising candidates for commercialization. Worldwide interest has prompted researchers to produce tens of thousands of studies on the topic, making PSCs one of the most active research topics of the past decade. Unfortunately, the rapid output of a substantial number of publications has made the traditional literature review process and research plans cumbersome tasks for both the novice and expert. In this dissertation, a data-driven analysis utilizing a novel text mining and natural language processing pipeline is applied on the perovskite literature to help decipher the field, uncover emerging research trends, and delineate an experimental research plan of action for this dissertation. The analysis led to the selection and exploration of two experimental projects on single-crystal PSCs, which are devices based on micrometers-thick grain-boundary-free monocrystalline films with long charge carrier diffusion lengths and enhanced light absorption (relative to polycrystalline films). First, a low-temperature crystallization approach is devised to improve the quality of methylammonium lead iodide (MAPbI3) single-crystal films, leading to devices with markedly enhanced open-circuit voltages (1.15 V vs 1.08 V for controls) and power conversion efficiencies (PCEs) of up to 21.9%, among the highest reported for MAPbI3-based devices. Second, mixed-cation formamidinium (FA)-based single-crystal PSCs are successfully fabricated with PCEs of up to 22.8% and short-circuit current values exceeding 26 mA cm-2, achieved by a significant expansion of the external quantum efficiency band edge, which extends past that of the state-of-the-art polycrystalline FAPbI3-based solar cells by about 50 meV — only 60 meV larger than that of the top-performing photovoltaic material, GaAs. These figures of merit not only set new record values for SC-PSCs, but also showcase the potential of adopting data-driven techniques to guide the research process of a data-rich field.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24228号 / 工博第5056号 / 新制||工||1789(附属図書館) / 京都大学大学院工学研究科マイクロエンジニアリング専攻 / (主査)教授 土屋 智由, 教授 平方 寛之, 教授 江利口 浩二 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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