A04: Surface Reactivity of Model Oxide Catalysts

Prof. Dr. Beatriz Roldán Cuenya

The goal of this project is the fundamental understanding of structure/reactivity/stability relationships for well-defined oxidation model catalysts in the liquid phase. We will perform surface-sensitive time-resolved operando studies for in situ grown epitaxial thin films, TFs (Co₃O₄, Fe₃O₄, CoFe₂O₄, VCo₂O₄ and LaCoO₃) and nanoparticle (NP) analogues during alcohol oxidation (electrocatalytic and thermal liquid-phase) and the electrocatalytic oxygen evolution reaction (OER). The epitaxial TFs ensure full experimental control and access to the surface properties on the atomic scale, while having the required conductivity for electrochemistry investigations. We will study the catalytic role of the surface orientation, of modifiers in a wide range of concentrations and of deliberately introduced defect motifs in order to elucidate their effect on the active state properties under reaction conditions. We will reveal how the catalyst (de)activates under reaction conditions and how the surface structure and the composition of the pre-catalyst affect this.

To this end we will apply surface-sensitive operando methodology such as grazing-incidence X-ray methods (X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD)) and (surface-enhanced) Raman spectroscopy. These studies will be backed up by in situ pre and post catalysis characterization using a variety of surface science methods like LEED, XPS/LEIS, AFM and STM. We will closely collaborate within the consortium to support and verify our findings with theoretical calculations and (operando) insights obtained by other groups. We expect to extend the knowledge we obtained during the 1^st funding period regarding structure-activity relationships for the initial pre-catalyst state by a deepened insight into the working catalyst’s operation mode, and progress towards a holistic understanding of the solid-liquid interface during oxidation catalysis under static and dynamic operation conditions.

(Figure: Left: STM image of Co₃O₄(111) and (B) Chronoamperometry data for Co₃O₄(111), Fe₃O₄(111) and CoFe₂O₄(111). Start current density: 1 mA/cm²; electrolyte: 0.1M KOH).