Reducible oxides play an important role in heterogeneous catalysis and electrocatalysis. Using a model catalysis approach, we explore fundamental mechanistic and kinetic phenomena on supported metal nanoparticles on reducible oxide supports.[1-4] Specifically, we consider Pt and Pd nanoparticles on well-defined cobalt oxide films. We show that the functionality of these interfaces is controlled by interactions between nanoparticle and support, such as electronic metal support interactions, spillover, and the formation of interface oxides. Surprisingly similar phenomena are observed when comparing heterogeneously catalyzed reactions and electrocatalytic reactions in liquid electrolytes. Under surface science conditions, we studied the geometric and electronic structure of model catalysts by XPS with synchrotron radiation, RPES (resonant photoemission spectroscopy), STM (scanning tunneling microscopy), IRAS (infrared reflection absorption spectroscopy), and TPD (temperature programmed desorption).[2] Specifically, we describe a new RPES method which allows us to monitor the oxidation state of cobalt with high accuracy.[3] We identify metal-support interactions and observe the dynamic formation of interface oxides for both Pt/Co3O4 and Pd/Co3O4. Finally, we probe the role of these effects on reactivity using simple test reactions. In the second step, we prepared atomically-defined oxide-based electrodes under surface science conditions and studied their properties in liquid electrolytes. Previously, we have shown that such model catalysts can be transferred into the electrolyte while preserving their surface structure.[1] Using in-situ electrochemical methods (CV, cyclic voltammetry; SCF, scanning flow cell experiments; EC-IRRAS, electrochemical infrared reflection absorption spectroscopy; EC-STM, electrochemical scanning tunneling microscopy; DEMS, differential electrochemical mass spectrometry), we explore particle size effects and metal-support interactions. Combining RPES and immersion-emersion EC-XPS,[4] we monitor dynamic oxidation and reduction of the nanoparticles and the Co3O4 support and explore the role of these redox processes for the electrocatalytic activity.

Model catalysis with reducible oxides: From surface science to the electrified interface

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.