The main aim of this thesis is the development of $^{17}$O solid-state nuclear magnetic resonance (NMR) spectroscopic techniques to study the local structure and ion dynamics of functional oxide materials for applications in energy conversion, in particular as electrodes and electrolytes in solid oxide fuel cells (SOFCs). Broadly, the work comprises two related areas: (1) application of a combined experimental and computational methodology to enable the first $^{17}$O solid-state NMR studies of paramagnetic oxides, in particular a class of perovskite-derived structures used as mixed ionic-electronic conductors (MIECs) for SOFC cathodes, and (2) further uses of multinuclear variable-temperature NMR spectroscopy, with emphasis on $^{17}$O NMR results, to elucidate mechanistic details of oxide-ion motion and sublattice exchange in a novel family of promising SOFC electrolyte materials based on $\delta$-Bi$_{2}$O$_{3}$. In the first section, $^{17}$O magic-angle spinning (MAS) NMR spectra of the paramagnetic MIEC, La$_{2}$NiO$_{4+\delta}$, are presented and rationalized with the aid of periodic DFT calculations. Advanced NMR pulse programming and quadrupolar filtering techniques are coupled to extract high-resolution spectra. In particular, these data reveal local structural distortions in La$_{2}$NiO$_{4+\delta}$ that arise from incorporation of interstitial oxide defects. Moreover, variable-temperature spectra indicate the onset of oxide-ion motion involving the interstitials at 130 °C, which is linked to an orthorhombic$-$tetragonal phase transition. By analyzing the ion dynamics on the spectral timescale, specific motional mechanisms are elucidated that prove relevant to understanding the functionality and conductivity of this phase. Next, a similar methodology is applied to the Sr-doped analogues, La$_{2-x}$Sr$_{x}$NiO$_{4+\delta}$, in an exploration of the defect chemistry and electronic structure of these phases (0 $\leq {x} \leq$ 1). By following the doping-induced evolution of spectral features assigned to interstitial and equatorial oxygen environments, changes in the ionic and electronic conductivity, respectively, are rationalized. This approach has been extended to the acquisition and assignment of $^{17}$O NMR spectra of isostructural Sm$_{2-x}$Sr$_{x}$NiO$_{4+\delta}$ and Pr$_{2-x}$Sr$_{x}$NiO$_{4+\delta}$ phases, promising SOFC cathode materials that exhibit paramagnetism on the A site (A = Sm, Pr). The final section details the characterization of oxide-ion motion in the fluorite-type phases Bi$_{1-x}$V$_{x}$O$_{1.5+x}$ and Bi$_{1-x}$P$_{x}$O$_{1.5+x}$ ($x$ = 0.087 and 0.148) developed as SOFC electrolytes. Variable-temperature NMR experiments between room temperature and 923 K reveal two distinct mechanisms. For the V-doped phases, an oxide-ion conduction mechanism is observed that involves oxygen exchange between the Bi-O sublattice and rapidly rotating VO$_{4}$ tetrahedral units. The more poorly conducting P-doped phase exhibits only vacancy conduction with no evidence of sublattice exchange, a result ascribed to the differing propensities of the dopants to undergo variable oxygen coordination. These initial insights suggest chemical design rules to improve the next generation of oxide-ion conducting materials.

Microporous metal organic frameworks (MOFs) are a novel class of materials formed through self-assembly of inorganic and organic structural building units (SBUs). They show great promise for many applications thanks to record-breaking internal surface areas, high porosity as well as a wide variety of possible chemical compositions. Molecular simulation has been instrumental in the study of MOFs to date, and this thesis work aims to validate and expand upon these efforts through two distinct computational MOF investigations. Current separation technologies used for CO2/N2 mixtures, found in the greenhouse gas-emitting flue gas generated by coal-burning power plants, could greatly benefit from the improved cost-effective separation MOF technology offers. MOFs have shown great potential for CO2 capture due to their low heat capacities and high, selective uptake of CO2. To ensure that simulation techniques effectively predict quantitative MOF gas uptakes and selectivities, it is important that the simulation parameters used, such as force fields, are adequate. We show that in all cases explored, the force field in current widespread use for N2 adsorption over-predicts uptake by at least 50% of the experimental uptake in MOFs. We propose a new N2 model, NIMF (Nitrogen in MoFs), that has been parameterized using experimental N2 uptake data in a diverse range of MOFs found in literature. The NIMF force field yields high accuracy N2 uptakes and will allow for accurate simulated uptakes and selectivities in existing and hypothetical MOF materials and will facilitate accurate identification of promising materials for CO2 capture and storage as well as air separation for oxy-fuel combustion. We also present the results of grand canonical and canonical Monte Carlo (GCMC and canonical MC), DFT and molecular dynamics (MD) simulations as well as charge density analyses, on both CO2 and N,N-dimethylformamide adsorbed in Ba2TMA(NO3) and MIL-68(In), two MOFs with non-equivalent inorganic structural building units. We demonstrate the excellent agreement found between our simulation results and the solid-state NMR (SSNMR) experiments carried out by Professor Yining Huang (Western University) on these two MOFs. Molecular simulation enables discoveries which complement SSNMR such as the number, distribution and dynamics of guest binding sites within a MOF. We show that the combination of SSNMR and molecular simulation forms a powerful analytical procedure for characterizing MOFs, and this novel set of microscopic characterization techniques allows for the optimization of new and existing MOFs.

Cette thèse porte sur la détermination et la modélisation, par la méthode PAW/GIPAW (Gauge Including Projector Augmented Waves), de paramètres RMN de fluorures inorganiques. Dans la première partie, une corrélation entre valeurs expérimentales de déplacements chimiques isotropes (diso) de 19F et de constantes d'écran isotropes (iso) de F calculées de fluorures binaires, dont les attributions sont triviales, est établie. Elle permet de prédire les spectres RMN de 19F avec une bonne précision. Les paramètres quadripolaires de ces fluorures sont aussi déterminés et calculés. Dans la seconde partie, la linéarité entre valeurs expérimentales de diso de 19F et valeurs calculées de iso de 19F permet une attribution non ambigüe des raies RMN de 19F de NbF5 et TaF5. Par contre, pour trois des quatre composés MF4 étudiés (b-ZrF4, HfF4, CeF4, ThF4), caractérisés par des gammes de valeurs de diso de 19F plus petites, les corrélations médiocres entre valeurs de diso et de siso de 19F ne le permettent pas. Enfin, NaAsF6 et KPF6 qui présentent des valeurs élevées de couplage 1J 19F-X et des transitions de phase à des températures proches de l'ambiante sont étudiés par DTA ou DSC et diffraction des rayons X sur poudre et RMN du solide multinucléaire à température variable. Les structures de a- et b-NaAsF6 sont déterminées. KPF6 adopte une structure de haute symétrie désordonnée à température ambiante mais les tentatives de détermination des positions atomiques des deux premières phases basse température sont restées vaines. Ce travail souligne les potentialités et quelques limites de cette méthode ainsi que l'attention qui doit être prêtée aux effets des optimisations. / This thesis focuses on the determination and the modeling, by the PAW/GIPAW (Gauge Including Projector Augmented Waves) method, of NMR parameters in inorganic fluorides. In the first part, a correlation between experimental 19F isotropic chemical shift (diso) and calculated 19F isotropic shieldings (siso) of binary fluorides with obvious assignments is established that allows to predict 19F NMR spectra with a good accuracy. The quadrupolar parameters of these fluorides are also determined and calculated. In the second part, a complete and unambiguous assignment of the 19F NMR lines of NbF5 and TaF5 is obtained, ensured by the linearity between experimental 19F diso values and calculated 19F siso values. On the other hand, for the studied MF4 (b-ZrF4, HfF4, CeF4, ThF4) compounds, characterized by smaller 19F diso ranges, except for ThF4, the poor correlations between experimental 19F diso and calculated 19F siso values prevent us to propose an assignment of the 19F NMR lines. In the last part, NaAsF6 and KPF6, exhibiting large 19F-X 1J-coupling and phase transitions at temperatures close to room temperature (RT) are investigated by DTA or DSC and variable temperature X-ray powder diffraction and multinuclear solid-state NMR. The structures of a- and b-NaAsF6 are determined. KPF6 adopts a disordered high symmetry structure at RT. Unfortunately, attempts to determine the atomic positions of the two first low temperature phases remain unsuccessful. This work highlights the potentialities and some limitations of this method as well as the care that must be taken when dealing with optimized structures.

Cocrystals have attracted much interest in recent years. It was once thought that cocrystals could be a means to prevent polymorphism but many recent examples of cocrystal polymorphism have been discovered and reported. In this contribution, we present a survey of polymorphic cocrystals. Polymorphism is the ability of a specific chemical compound to crystallize in more than one crystalline form. Polymorphs have different arrangements of the molecules in the given crystal lattice and may exhibit different characteristics such as packing properties, thermodynamic properties, spectroscopic properties, kinetic properties, surface properties, and mechanical properties. Polymorphs can be classified in various groups such as crystalline, amorphous, hydrates, and solvates. The main characterization methods used in this thesis are X-ray diffraction and solid-state NMR spectroscopy. The concept of variable stoichiometry cocrystallization is explored in halogen-bonded systems. Three novel cocrystals of 1,4-diiodotetrafluorobenzene and 3-nitropyridine with molar ratios of 1:1, 2:1, and 1:2, respectively, are prepared by slow evaporation methods. Powder X-ray diffraction experiments carried out on the 1:1 and 2:1 cocrystals confirm that gentle grinding does not alter the crystal forms. 1H → 13C and 19F →13C cross-polarization magic angle spinning (CP/MAS) NMR experiments performed on powdered samples of the 1:1 and 2:1 cocrystals are used as spectral editing tools to select for either the halogen bond acceptor or donor, respectively. I also describe the formation of a new cocrystal of 1, 3, 5-trifluoro-2, 4, 6-triiodobenzene and piperazine with a 2:1 molar ratio that was prepared by the slow evaporation method. In addition of that, I have prepared the cocrystal (1,4- VII diiodotetrafluorobenzene)(coumarin ) already reported. After preparation and purification process of this compound, I obtained a small amount powder, but could not characterize it by solid-state NMR; rather I performed powder X-ray diffraction to study this compound. Overall, this work contributes new examples to the field of polymorphism in halogen-bonded systems and to variable stoichiometry cocrystal engineering with halogen bonds.

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This body of work is tackling some of the challenges in the field of lithium-ion batteries (LIBs) for electric vehicles through in situ nuclear magnetic resonance (NMR). In situ NMR allows for the simultaneous monitoring of both liquid and solid components (electrolyte, cathode, anode, separator) and provides timely data acquisition making it a great method to extract real-time information about structural changes, degradation products and failure mechanisms in batteries. A combined in situ 7Li NMR and ex situ 29Si magic-angle spinning (MAS) NMR study on silicon and silicon monoxide was used to compare structural differences in these anode materials using a custom-made in situ cell. Some key differences between the two materials were obtained, highlighting the importance of in situ NMR to be used for identifying phases, which are not present under ex situ conditions. In addition, fast charging of silicon anodes was investigated to gain a better understanding of their performance at high current rates. Magnetic resonance imaging was also implemented to localize lithium metal deposition under these conditions, which was made possible by a unique in situ parallel-plate resonator setup. Finally, the successful development of a novel in situ MAS NMR technique is introduced, which for the first time allows for an in situ analysis of a LIB under MAS. This strategy paves the way toward acquisition of valuable in situ data on the formation and transformations of metastable states within the active materials of both electrodes; data that is difficult to obtain from static in situ NMR experiments alone. / Thesis / Doctor of Philosophy (PhD)

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