The main subject of this thesis is a practical elaboration of the subject "Boron, Carbon and Nitrogen Group of the p-block elements" in form of presentations created using the Microsoft PowerPoint program. The presentations are designed to be used in practice, during the education of chemistry at secondary schools. The thesis also contains additional comments for teachers and an analysis of curricular documents and selected textbooks. It is elaborated in accordance with the RVP G programme.

Parmi les défis que le Monde devra affronter dans les prochaines décennies, le plus difficile est l’utilisation d’énergie durable. Dans un scénario où les sociétés occidentales sont fortement dépendantes des combustibles fossiles pour garder leur niveau de bien-être (chauffage domestique, transport et production d’électricité), complété par les pays en voie de développement qui ont besoin d’alimenter leurs économies croissantes, il est nécessaire de souligner l’impact négatif sur l’environnement causé par l’utilisation de ces ressources fossiles mais aussi les problèmes géopolitiques pour les pays « non producteurs ». La collecte d’énergie provenant des sources renouvelables peut limiter la dépendance des combustibles fossiles, pourtant cette dernière ne peut remplacer les centrales électriques classiques à cause de son caractère intermittent.Les batteries sont des dispositifs qui peuvent résoudre définitivement cette limitation, puisqu’elles sont capables d’accumuler l’excès d’énergie produit afin de le délivrer au moment souhaité. De plus elles ont été envisagées comme les dispositifs principaux pour toutes les applications portables (téléphones et ordinateurs portables mais aussi véhicules). Grâces à ses excellentes performances et sa technologie bien développée, les batteries lithium-ion ont un rôle déterminant dans le support de cette nouvelle révolution énergétique. Pourtant leur usage répandu a été récemment remis en question à cause de la faible disponibilité de lithium, qui est un élément rare et concentré seulement dans certaines zones du monde. L’emploie du lithium pourrait donc engendrer les mêmes problèmes que les combustibles fossiles. De plus, cette technologie semble avoir atteint son niveau de développement maximal et ne pourrait plus être suffisante pour satisfaire des applications de plus en plus énergivores. Il est donc nécessaire d’envisager des alternatives au lithium en axant les recherches sur des ressources plus abondantes que lithium et à moindre coût mais aussi sur des systèmes plus performantes.Les batteries post-lithium, qui sont basées sur d’autres porteur de charges que le Li+, pourrait représenter des alternatives plus sécurisées, respectueuse de l'environnement et aussi plus attractifs en termes de capacité stockée. Le magnésium est un candidat prometteur pouvant remplacer le lithium dans les systèmes électrochimiques de stockage d’énergie, grâce à son abondance, son faible coût et sa capacité volumique qui est doublée par rapport à cette du lithium. Cependant, l’obstacle le plus important au développement des batteries rechargeable au magnésium est la mauvaise compatibilité entre les électrolytes classiques et le magnésium métal. Dans cette optique il est encore nécessaire d’utiliser des mélanges de sel/solvant extrêmement dangereux dans les prototypes proposés. En revanche, la recherche de possible alternatives au magnésium métal, c.-à-d. des matériaux capable de réagir à bas potentiel avec le Mg, permettrait de réaliser une véritable batterie aux ions de magnésium (MIB), compatible avec des formulations d’électrolyte classiques.Cette thèse est dédiée à l’investigation des comportements électrochimiques de plusieurs éléments du bloc p (In, Sn, Sb, Bi) qui peuvent s’allier réversiblement avec le Mg à bas potentiel. Des possibles synergies entre ces éléments ont été aussi explorées (composite Sn-Bi, phases intermétalliques BixSb1-x et InBi) qui puissent être employés comme électrodes négatives pour MIBs. Des poudres micrométriques ont été obtenues par broyage/alliage mécanique, technique de synthèse simple à mettre en œuvre. Une attention particulière a été portée à l’étude des mécanismes électrochimiques d’alliage et/ou conversion avec la diffraction des rayons X en mode operando. L’évaluation des performances électrochimiques a permis de sélectionner le meilleur candidat pour être testé comme électrode négative dans un prototype de batterie magnésium-ion. / One of the most challenging hurdles that the World has to face in the next decades is the sustainable use of energy. In a scenario where western societies are largely dependent of the fossil fuels for maintaining their wellness, i.e. for heating, automotive transportation and electricity production, and developing countries need to feed their growing economies, it is worth underlying both the major impact on the environment due to the indiscriminate use of such combustibles but also the geopolitical issues for the non-producing countries. Energy harvesting by renewable sources can help limiting the dependence on fossil fuel exploitation but cannot perfectly replace conventional power plant due to its intrinsic intermittency.Batteries are the devices that can draw a line under this situation, since they can stock the energy surplus when the plant is operating and then can squeeze it in the power grid when there is a lack of production. Moreover, they are also targeted to fulfil the even growing demand of energy for portable applications (mobile phones and computers, and nowadays cars and trucks). The excellent performance and the well-established technology of Lithium-ion batteries (LIBs) put them in a crucial position for supporting this new energy revolution. However their ubiquitous role has been recently questioned for two main reasons: i) of the low availability of Li, which is a rare and not-uniformly spread element that may lead to the similar problems caused by fossil fuels. And ii) the effective capacity to satisfy the highly energy-demanding applications, since Li-ion technology seems reaching is upper limit in terms of overall performance. Therefore cheaper and more powerful alternative to Li-based systems are needed.Post-Lithium-based batteries, based on other charge carriers than Li+ can be offer safer, more sustainable and performing alternative to LIBs. Mg is a promising candidate that can replace Li in electrochemical systems due to its abundance, low cost and a theoretical volume capacity twice higher than that of Li. Although the efforts devoted to the realization of a rechargeable Mg battery were made in the last 15 years, the major hurdle represented by the low compatibility between metallic Mg and conventional electrolytes still obliges the use of hazardous salt/solvent mixtures in research prototypes. Searching alternative negative electrodes to the Mg metal, i.e. compounds able to reversibly react with Mg at low potential, will pave the way for a veritable Magnesium-ion battery (MIB), allowing the use of conventional electrolytes.The present thesis is devoted to investigate the electrochemical behaviour of several p-block elements that can reversibly alloy with Mg at low potential (In, Sn, Sb, Bi). Possible synergies between these elements are also explored, realizing composite materials (Sn-Bi), or intermetallic phases (BixSb1-x and InBi) that could be employed as negative electrodes in MIBs. The chosen synthetic route for obtaining micrometric-sized particles is the mechanical milling/alloying, since it is simple, cost-effective and upscalable. Particular attention is put on the study of electrochemical mechanisms through the operando X-ray diffraction. Electrochemical performance evaluation allows selecting the best candidate for an effective test as negative electrode in MIB prototype.

Coordination chemistry usually applies to transition metals, but has recently been extended to the p-block elements. For the pnictogen atoms (group 15), this type of coordination chemistry has already been applied to antimony and bismuth, where they behave as Lewis acceptor centres. However, complexes with nitrogen and phosphorus as Lewis acidic centres are rare, due to their relatively small atomic radii and inherent basic nature. Instead, these elements (Pn(III)) are typically observed as donor centres because they are better at donating their electron pair, than they are at accepting them. To enhance the Lewis acidity at the phosphorus and nitrogen centres, a cationic charge can be introduced by heterolytically abstracting a halide and replacing it with a weakly coordinating anion, providing more opportunities for new reactivity. The presence of a stereochemically active lone pair at the acceptor site also introduces new reactivity patterns to be explored. The formation of these main group coordination complexes opens doors to potential applications in catalysis, small molecule activation, or as material precursors. 2,2’-bipyridine (bipy) has been a prototypical ligand used in transition metal coordination chemistry due to its high basicity and oxidative resistance. This property has been exploited to enable a comprehensive study of a series of Pn(III) tricationic and dicationic complexes using 2,2’-bipyridine (bipy); 4,4’-di-tert-butyl-2,2’-bipyridine (tBu2bipy); 4-dimethylaminopyridine (DMAP); and other main group containing ligands. / Graduate

The development of a clean hydrogen economy will aid a smooth transition from fossil fuels which is required to stem the environmental impact and economic instability caused by oil dependency. For vehicular application, in addition to being cheap and safe, a commercial hydrogen store must contain a certain weight percentage of hydrogen to provide a reasonable range (~300 miles). It must also be able to release hydrogen under near-ambient conditions (80-120°C) and have a reasonable cycling capacity (~1000 cycles). The primary motivation of this thesis is to gain a fundamental understanding into the sorption processes of hydrogen on carbon- and aluminium-based materials to improve their hydrogen storage capacity. The sorption processes of hydrogen on mechanically milled graphite have been investigated, primarily using Electron Spin Resonance Spectroscopy and Inelastic Neutron Scattering. An investigation into the storage properties of tetrahydroaluminates, primarily NaAlH₄ and LiAlH₄, is performed in the presence and absence of a catalyst, and a new phase of NaAlH₄ is observed prior to its decomposition. Variable temperature neutron and synchrotron diffraction, in conjunction with gravimetric and mass spectroscopy data were obtained for several mixtures of tetrahydroaluminates and alkali amides and the hydrogen desorption processes are shown to be quite different from the constituent materials. The structure of Ca(AlH₄)₂ has been experimentally determined for the first time and a complete set of equations describing its decomposition pathway is given.