The increased demand for electric vehicles in recent years has driven the development of Li ion battery technology, yielding interesting trends in cathode materials. The layered cathode material Li(Ni1/3Mn1/3Co1/3)O2 gives 30% more reversible lithium extraction than the earlier LiCoO2 and the “overlithiated” material Li(Li0.2Mn0.54Ni0.13Co0.13)O2 gives a semi-reversible capacity 25% higher than Li(Ni1/3Mn1/3Co1/3)O2.1,2 6,7Li MAS NMR and 7Li MATPASS NMR were used to investigate the relation between the lithium ion and metal positions within these materials. It was found that Li(Ni1/3Mn1/3Co1/3)O2 showed a preference for Li ions to associate with Co at high voltages, that Mn4+ and Ni2+ showed some association and that the metals were not highly ordered. Li(Li0.2Mn0.5Ni0.13Co0.13)O2 showed a decrease in transition metal layer lithium upon cycling, in agreement with previous models, an ordering of the metal ions with the reinsertion of the lithium ions and a significant change in structure on deep discharge.3 These results will hopefully lead to more accurate modelling of the materials, understanding of reversibility and to increased reversible capacities in future cathode materials. Additionally work was done to enable high rate in-situ NMR spectra in which spectra are obtained from a cell while cycling in the bore of an NMR spectrometer. A Teflon Swagelok-style cell was designed and the effectiveness of solenoid and saddle coils were tested. It was found that for a 6 mm diameter cathode with a Li metal anode, at least half of the signal intensity could be obtained with a saddle coil whereas the signal was not detected when using a solenoid coil. / Thesis / Master of Science (MSc)

Carbon dioxide electroreduction (CO2R) is a promising and sustainable route to generate valuable feedstocks through the electrochemical conversion from CO2 with electricity generated by renewable energy resources, to reduce greenhouse gas emissions, thereby protecting the global environment. One of the critical challenges for developing practical CO2R developments is understanding the structures and chemistry of CO2R electrocatalysts, and then generating fundamental insights to guide the design and optimization of high-performance electrocatalysts. During my Ph.D. studies, synchrotron-based X-ray spectro-microscopy techniques, scanning transmission X-ray microscopy (STXM) and X-ray spectro-ptychography, were used to study nickel-nitrogen-carbon (Ni-N-C) and electrodeposited Cu-based CO2R electrocatalysts. STXM and ptychography were upgraded to in situ characterizations to provide spectroscopic characterization and quantitative, chemically selective imaging of these catalytic materials under CO2R conditions. To achieve in situ STXM and spectro-ptychography, a micro-fluidic based, liquid-flow electrochemical in situ device was developed, fabricated, and implemented. The in situ device is optimized from previous versions developed by Vinod Prabu, past graduate student of Hitchcock group, and the initial concept was provided by Pablo Ingino and Dr. Martin Obst, collaborators at the University of Bayreuth. In situ STXM and spectro-ptychography provided a detailed chemical and morphological evaluation of catalyst materials at different applied potentials during electrochemical processes. The in situ STXM studies of Cu-based catalysts showed that electrodeposited Cu2O particles are converted to metallic Cu with different reaction rates at applied potentials less negative than that for initiation of CO2R. The in situ STXM results show a degree of heterogeneity in the electrochemical response of discrete nanoparticles and metallic Cu as the active catalyst for CO2 reduction which is structurally relatively stable at CO2R-relevant potentials within the spatial resolution of STXM. In situ spectra-ptychography was used to follow morphological changes of a single Cu-based catalytic particle in the electrochemical regime of CO2R. Our results show that the Cu particle lost the initial cubic structure and formed irregular dendritic-like structures during the CO2R process. To the best of my knowledge, this is the first time in situ STXM has been applied to CO2R electrocatalysts under flow liquid and electrochemical conditions and the first report of in situ spectro-ptychography studies. In summary, my research has successfully achieved the in situ STXM and spectro-ptychography experiments and contributed to an improved understanding of Cu nanoparticle CO2R electrocatalysts. / Dissertation / Doctor of Philosophy (PhD)

Per- and polyfluoroalkyl substances (PFAS) are a rising topic in the field of contaminated sites around the world, with destruction of these being an area in dire need of innovation. Previous experiments of destructive character have been proven efficient using boron doped diamond electrodes (BDD) in small scale electrochemical cells. Further need for experimentation on actual site conditions is needed to further evaluate the use of this method, as well as research on alternative electrode materials to reduce the cost of remediation.  In this study, four cells containing contaminated soil were used: one with BDD electrodes, one with iron electrodes and two control cells. The iron electrodes were used to investigate if a less costly electrode material could achieve any degree of PFAS degradation. For the experiment a soil from a previous firefighting training site where firefighting foam containing high amounts of PFAS (620                     g/kg soil concentration) was used. During the first phase of the experiment a constant flow of deionized water was added to the cells containing the soil, and porewater was sampled at the in- and outflow along with the soil porewater, on a weekly basis, to evaluate the distribution of PFAS to provide information about possible degradation taking place. The extent of degradation was not quantified. However, due to differences in the molecular composition of the analysed PFAS a trend where short-chain PFAS increase throughout the experiment in the BDD cell indicated that short-chain PFAS were generated, which is an expected by-product in electrochemical oxidation of PFAS. No short-chain PFAS generation was seen in the iron electrode cell, nor was there a high amount present in the control cell leachate.  Further, leaching of PFAS was more efficient in the control cells, while PFAS in the BDD and iron electrode cell were retained or leaching was slowed down, most likely due to the electrode interaction with PFAS in porewater.Additionally a second phase where water flow through was halted and the cells were run in a batch mode was conducted to see PFAS degradation in stagnant conditions over time. In the stagnant cell in the second phase, only low PFAS concentrations in porewater were recorded while no degradation was established.  Further, fluoride analysis recorded F- concentrations in the range of    M, where the limit of detection was   M, which limited the confirmation of PFAS mineralisation in soil.  From this study insight of the difficulties with soil treatment of PFAS using electrokinetic method was highlighted, with sampling being a key factor in the accuracy of the result. For a more accurate establishment of the degradation experiments in a closed cell, with more extensive sampling throughout the entire column would be necessary. This is needed to generate a clearer picture of changes in PFAS concentration in the soil from the presumed degradation, coupled with a mass balance to provide the fate of PFAS in this type of setup.

Petroleum spills cost large sums of money to remediate, which has resulted in the use of more in-situ technologies, including chemical oxidation, as cost effective alternatives to traditional methods of remediation. There are numerous case studies documenting the success of hydrogen peroxide as an in-situ oxidizer in that regulated BTEX concentrations were lowered below target cleanup levels. Little information is available; however, regarding the behavior of petroleum hydrocarbons post injection of hydrogen peroxide or what chemical derivatives may be produced as a result of the oxidation process. Laboratory protocols have been employed to yield data regarding the behavior of BTEX specifically, and all volatile gasoline constituents in general, over a period of time post injection of hydrogen peroxide. The results of the data indicate variations in petroleum compound behavior are predicated on the concentration of hydrogen peroxide, the degree of contamination, and the presence of a soil matrix.

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