The present study focuses on the development of Al-based systems and their examination as a medium for reversible hydrogen uptake. The first part of this thesis is dedicated to the chemistry and properties of Al-N-based materials. The synthesis, characterization, and detailed thermal decomposition studies of several aminoalanes have been described. As a result, single-crystal X-ray diffraction analyses revealed two new crystal structures of piperidinoalanes. The perspective approach employing activated aluminum and piperidine for reversible hydrogen uptake has been established. The second part of this work was focused on the modification of the properties of NaAlH4-based systems in order to generate the material with the high dissociation pressure suitable for high-pressure tank technologies. Considerable progress has been achieved in improving the hydrogen sorption properties by adding the extra aluminum powder to the Ti-catalysed NaAlH4-based system. Thus, the present study contributes to the understanding of the hydrogen sorption behavior of Al-based systems with perspectives being applicable to other related materials.:DECLARATION ACKNOWLEDGEMENTS DEFINITIONS AND ABBREVIATIONS ABSTRACT CONTENTS LIST OF TABLES LIST OF FIGURES MOTIVATION AND GOALS 1 INTRODUCTION 1.1 The prospects for hydrogen-based energy systems 1.2 Requirements for the hydrogen storage system 1.3 An overview of hydrogen storage strategies 1.4 Complex hydrides as a promising hydrogen storage materials 1.4.1 Metal borohydride systems 1.4.2 Alanate-based systems 1.4.3 Nitrogen-containing complex hydrides 1.5 Summary 2 GENERAL CHARACTERIZATION METHODS 2.1 X-ray crystallography 2.1.1 X-ray powder diffraction (XRPD) 2.1.2 Single-crystal structure analysis 2.2 Thermal analysis 2.3 Quantitative chemical analysis 2.3.1 Elemental analysis 2.3.2 Inductively coupled plasma optical emission spectrometry (ICP-OES) 2.4 Nuclear magnetic resonance spectroscopy (NMR) 3 LIQUID-STATE HYDROGEN STORAGE 3.1 State of the art 3.1.1 Liquid-state hydrogen storage materials 3.1.2 Al-N-based compounds as potential materials for hydrogen storage 3.1.3 Summary 3.2 Materials preparation and experimental details 3.2.1 Chemicals and sample handling 3.2.2 Synthesis of aminoalane in diethyl ether solution with aluminum hydride 3.2.3 Preparation of activated aluminum 3.2.4 Direct hydrogenation of activated aluminum supported by amine 3.3 Results and discussion 3.3.1 Is the solid-state hydrogen storage in aminoalanes possible? 3.3.2 Optimization of the direct hydrogenation of activated aluminum supported by amine 3.3.2.1 Synthesis and characterization of triethylenediamine alane complex 3.3.2.2 Synthesis of aminoalanes via direct hydrogenation of activated aluminum and N-heterocyclic amine 3.3.3 Investigation of piperidinoalanes for reversible hydrogen uptake 3.3.3.1 Crystal structure determination of piperidinoalanes 3.3.3.2 Influence of the initial reaction parameters on the piperidinoalane formation 3.3.3.3 Reversible hydrogenation in piperidinoalane system 3.3.4 Conclusions 4 SOLID-STATE HYDROGEN STORAGE 4.1 State of the art 4.1.1 Thermodynamic tuning of the hydrides 4.1.2 Features of the sodium alanate system 4.1.3 Catalytic enhancement of reversible hydrogenation in sodium alanate 4.1.4 The relevance of the Al-TM species in doped sodium alanate 4.1.5 Summary 4.2 Materials preparation and experimental details 4.2.1 Chemicals and purification procedure 4.2.2 Activation procedure of sodium alanate via mechanochemical treatment 4.2.3 Pressure-composition-isotherm measurements with a Sieverts-apparatus 4.2.4 High-pressure differential scanning calorimetry investigation of sodium alanate samples 4.3 Results and discussion 4.3.1 Tailoring the properties of sodium alanate-based system with the help of Ti-additive 4.3.2 Influence of the aluminum addition on the sorption behavior of Ti-doped sodium alanate 4.3.3 High-pressure DSC study of hydrogen sorption properties of doped sodium alanate system 4.3.4 Conclusions 5 SUMMARY AND CONCLUSIONS RECOMMENDATIONS AND OUTLOOK REFERENCES SUPPORTING INFORMATION Appendix A Appendix B Appendix C Publications

Im Rahmen des BMBF-Projektes 'RevAl' wurden bereits bekannte Aminoalane in Bezug auf ihre physikalisch-chemischen Eigenschaften bei der chemischen Wasserstoffspeicherung untersucht. Es stellte sich heraus, dass die Freisetzung von Wasserstoff leicht und spontan realisierbar ist, wohingegen die reversible Speicherung (aufgrund von thermodynamischen Gesetzmässigkeiten) bei den gewählten Prozessbedingungen nicht realisierbar ist. Auch Modifikationen der bereits bekannten Aminoalane mit Neutralliganden und organischen Resten führten nicht zu den erhofften Eigenschaften. Jedoch wurde im Rahmen der Modifizierungsarbeiten die noch nicht beschriebene Verbindung 'Bis-Triphenylphosphinalan' strukturell und spektroskopisch charakterisiert. Weiterhin wurde diese im 9g-Maßstab hergestellte Verbindung für Reduktionsreaktionen von Carbonylderivaten eingesetzt, wobei sich, abhängig vom jeweiligen Carbonyl-Substrat, Unterschiede bei Umsatz und Ausbeute der Edukte bzw. Produkte ergaben. Weiterhin wurde die Reduktion von Benzaldehyd mit Bis-Triphenylphosphinalan NMR-spektroskopisch untersucht und eine Untermauerung des bereits postulierten Reduktionsmechanismus´ erhalten.