Abstract
Mass transport is crucial in heterogeneous catalysis, affecting activity, selectivity, and catalyst lifespan. Rational pore space design can significantly enhance catalytic performance. Therefore, high-resolution and high-throughput porosity characterization techniques are needed to study how synthesis parameters influence catalyst pore networks. However, current techniques face challenges: bulk measurements overlook heterogeneity, while high-resolution methods are complex, costly, and offer poor statistical representation. This PhD thesis explores new analytical methods using X-ray and fluorescence microscopy. Chapter 2 utilizes transmission X-ray microscopy (TXM) to study macroporosity in MIL-47(V) MOF crystals, revealing the presence of poorly connected macropore defects. Chapter 3 introduces a cost-effective method using fluorescence microscopy and a PDMS-made microfluidic device to characterize individual porous particles, showing significant inter-particle heterogeneities. Moreover, the mass transport within the porous particles could be tuned by varying the pH and ionic strength of the system. Chapters 4-6 focus on single-molecule localization microscopy (SMLM) and single particle tracking (SPT) for sub-diffraction limit resolution mapping. Chapter 4 presents a 2D silica model pore system to study quantum dot (QD) motion behavior. Probe trapping on the pore walls was found to be pH dependent. Using high pH suppressed QD immobilization and allowed the fluorescent probes to explore the pore space of a real catalyst. Chapter 5 investigates 3D pore size probing via local diffusion coefficients of individual QDs tracked in 2D. Contrary to hydrodynamic drag simulations, constant diffusion coefficients were observed when the pore dimensions were varied. Chapter 6 uses smaller carbon dot probes (~2 nm) for pore-space exploration, revealing their potential to map mesoporous materials and chemically heterogeneous surfaces.
Original language | English |
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Qualification | Doctor of Philosophy |
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Award date | 1 Jul 2024 |
Place of Publication | Utrecht |
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Publication status | Published - Jul 2024 |