Bridging the Material and Pressure Gap for Oxidic Catalysts: Unraveling the Structure-Activity Relationships of Cerium Oxide in the (Reverse) Water Gas Shift Reaction

• Applicant: Professor Dr. Christof Wöll
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544145964

This groundbreaking project combines expertise in model catalysis, multifunctional catalytic material engineering, and machine learning, offering a unique chance to propel the rational design and understanding of ceria-based catalysts. The focus is on developing catalysts showcasing heightened activity, superior selectivity, and stability. The aim is to establish a profound understanding of the intricate relationship between catalyst structure and performance: Unraveling the active phase, potential active sites, their architectural configuration, and their role in forming surface species for the studied. In heterogeneous catalysis on solid surfaces, surface composition, electronic structure, and geometric features intricately shape catalytic properties. While single-crystal-based model catalysts provide fundamental insights under ultrahigh-vacuum (UHV) conditions, the challenge resides in bridging the 'materials gap' and 'pressure gap' between single crystals and practical powder catalysts operating at atmospheric pressures. Nanocrystals with uniform composition and structure emerge as a viable solution, forming a bridge between single crystals and powder catalysts. Ceria nanoshapes, particularly with their varying morphologies, present an ideal platform to explore morphology-dependent catalytic properties. Cerium oxide, renowned for redox properties and high oxygen storage capacity, has extensive applications, including three-way catalysts, H2 purification through CO oxidation, low-temperature water-gas shift (WGS) reaction, and reverse water-gas shift (RWGS) reaction. The (reverse) WGS reaction, a focal point of this project, holds promise for connecting the worlds of single crystals and powder catalysts. The research pursues two major avenues: model catalysts based on single crystals and 'real' catalysts in powder form. The former involves characterizing macroscopic oxide single crystals using XPS, LEED, NEXAFS, with a meticulous study focusing on relevant adsorbates (H2O, CO, CO2, -OH) on ceria using IRRAS. Simultaneously, the synthesis of powder materials includes creating nanocubes, nanooctahedra, and nanorods of CeO2, alongside polycrystalline CeO2 powder. Structural and physicochemical characterization involves traditional techniques (N2 physisorption, XRD, HRTEM), followed by detailed adsorption studies using the mentioned adsorbates and different infrared spectroscopy variants from compatible UHV to 1 mbar in transmission mode (80-800K). Additionally, DRIFT mode enables working up to 1 bar for operando studies of the (R)WGS reaction. Exploring the intricate chemical nature of true reaction intermediates in metal (Pt or Cu)-supported ceria catalysts under working conditions will involve the use of advanced techniques like modulated excitation spectroscopy with phase-sensitive detection. Furthermore, the project introduces cutting-edge deep learning models to predict structures from infrared spectra, enhancing predictive capabilities.

• DFG Programme: Research Grants
• International Connection: Argentina
• Partner Organisation: Consejo Nacional de Investigaciones Científicas y Técnicas
• Cooperation Partners: Dr. Alejo Aguirre; Professor Dr. Adrian Bonivardi; Professor Dr. Matias F. Gerard; Professor Dr. Diego H. Milone; Dr. Julia Vecchietti
• Co-Investigator: Dr. Alexei Nefedov