Ceria-Based Single-Atom Catalysts: From Simplified Models Towards Real-World Complexity

In recent years, single atoms have emerged as a new paradigm in catalysis, promising numerous advantages over traditional approaches. Despite the growing potential for industrial application, the precise structure of the active site is often still poorly understood. In addition, at the atomic scale, dynamic effects become ubiquitous and influence reactivity. This thesis approaches these issues for ceria-based single-atom catalysts with various transition metals as active centers. Via Density Functional Theory modelling, atomic structures are resolved, local polaron distributions explored, and electron transfer dynamics between the isolated metal atoms and the surface investigated, proving their ubiquity in ceria-based systems. Moreover, the influence of surface reduction as the most common chemical modification of ceria, is addressed, showing how uncommon metal oxidation states can be made accessible via the electronic interaction with the support. The obtained wealth of data is further used to construct predictive machine learning models that provide additional physical insight into the metal-support interaction. In collaboration with experimental groups, surface peroxide is identified as the origin of the exceptionally high stabilization capability of oxygen plasma pretreated ceria for atomically dispersed platinum. Lastly, the reactivity landscape for ammonia oxidation to nitrous oxide is explored for a ceria-based manganese catalyst, allowing to rationalize its high catalytic performance via a thermodynamically favorable catalytic cycle. The results prove the pivotal role of ceria as a non-innocent support, influencing atomic structure, dynamic behavior, and reactivity. They present a further step towards atomically precise control in single-atom catalysts, desperately needed for industrial application.

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