Atomic Resolution Electron Microscopy of Nanoparticles for Catalysis

Catalysis is central in advancing sustainable energy systems by accelerating chemical reactions and unlocking new reaction pathways for energy conversion and storage. Catalyst functionality arises from interactions between reactant molecules and the catalyst surface structure. While nanoparticles offer high catalytic efficiency due to their abundance of exposed sites, the structure–function relationship lacks comprehensive understanding, necessitating atomic-scale characterization to guide catalyst design. This thesis leverages recent advances in transmission electron microscopy (TEM) to visualize and quantify the three-dimensional atomic structure of catalytic nanoparticles.

This work focuses on the experimental retrieval of exit waves from focal series of brightfield TEM images which maximize information per electron. To preserve structural integrity of under coordinated surface atoms that are particularly prone to beam-induced alterations compared to bulk materials, imaging is performed at low electron dose rates in combination with direct electron detectors. This ensures high resolution imaging without compromising the pristine state of the material.

Exit wave reconstruction methodology is advanced by implementing a 50 pm-resolution microscope equipped with an open gas cell, enabling atomic-scale imaging under reactive conditions. This instrument allows direct visualization of surface restructuring and molecular adsorption on catalytic nanoparticles in relevant gas and temperature environments. The superior lateral resolution and z-axis stability of this microscope enhance structural analysis of nanoparticles aligned along high-symmetry axis. By analyzing the experimentally reconstructed exit waves using channeling theory, three-dimensional atomic structure is extracted.

This thesis presents a TEM-based strategy that integrates experimental advances with analytical interpretation to uncover how catalyst structure relates to function.