01. PhD Thesis

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Browsing 01. PhD Thesis by Author "Karibayev, Mirat"

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    MULTISCALE MODELING OF CHEMICAL STABILITY AND TRANSPORTATION OF OH- ION FOR CHITOSAN-BASED BIOCOMPOSITE ANION EXCHANGE MEMBRANE FUEL CELLS
    (Nazarbayev University School of Engineering and Digital Sciences, 2024-08) Karibayev, Mirat
    Anion Exchange Membrane Fuel Cells are obtaining popularity in current research due to their promising advancements, which include low production costs, the ability to use catalysts free of platinum group metals, moderate operating temperatures, and high power densities. However, the primary challenge of Anion Exchange Membranes is associated with chemical instability of the quaternary ammonium head groups in alkaline conditions and elevated temperatures, which also led to a decrease in the diffusion of hydroxide ions. This study used Density Functional Theory calculations, ab initio Molecular Dynamics simulations, and conventional all-atom Molecular Dynamics simulations to examine the chemical stability of different chemical structures, including quaternary ammonium head groups, quaternized chitosan head groups, and Deep Eutectic Solvent supported quaternized chitosan head groups as well as the diffusion of hydroxide ions. This research work consisted of the following four main objectives: i) the degradation mechanisms of different quaternary ammonium head groups under different hydration levels via the Density Functional Theory method, ii) the diffusion of hydroxide ion via different quaternary ammonium head groups under different hydration levels via conventional all-atom Molecular Dynamics simulations, iii) the degrataion mechanisms of various quaternized chitosan head groups and the diffusion of hydroxide ions under different hydration levels and temperatures via the Density Functional Theory method and conventional all-atom Molecular Dynamics simulations, and finally iv) explore the degradation mechanisms and diffusion mechanisms of hydroxide ion via Deep Eutectic Solvents supported tetramethylammonium head group and quaternized chitosan head group under different hydration levels and temperatures via Density Functional Theory calculations and ab initio Molecular Dynamics simulations....