Heterogeneous Oxidation Catalysis in the Liquid Phase

B06: Correlative and Multi-Modal Quasi In Situ and Operando Spectroscopy and Microscopy

Prof. Dr. Serena DeBeer • Dr. Thomas Lunkenbein

This project focuses on the influence of (frustrated) phase transitions on the performance of spinel- and perovskite-type catalysts in liquid phase oxidation reactions. This concept well explored for thermal gas phase reactions and oxygen evolution reaction (OER) over metallic and oxidic surfaces has yet not been correlatively and systematically tackled in thermal and electrochemical liquid phase oxidation of alcohols interacting with (solvated) surfaces.

We will follow the geometric and electronic changes that occur during catalysis and correlate the results from thermal gas and liquid phase oxidation of alcohols, with results obtained from electrochemical alcohol oxidation and OER. This correlation will allow us to determine common structural features that optimize catalytic performance. The catalysts used for OER will act as structural references. The selected experimental portfolio enables correlative operando and quasi in situ analyses. Our correlative multi-modal approach is based on electron and X-ray spectroscopy and microscopy, as well as electron paramagnetic resonance spectroscopy. Combining the outcome of these complementary techniques will ultimately lead to improved structure-performance correlations. In addition, we will explore the role of promoters on chemical dynamics. Changes in the geometric and electronic structures include morphology and crystallography, oxidation states, oxygen vacancies and radical concentrations. These results will provide important input for the theory projects in order to derive a more detailed understanding of the reaction mechanism.

(Figure: Frustrated phase transition. Under non-optimal reaction conditions, phase A (left) transforms into phase B (right). Under ideal reaction conditions, characterized by highest activity or selectivity, the catalyst is trapped in an energetically excited state just before the phase transformation (middle)).