High-Pressure Cell for In Situ Grazing Incidence XAS Characterization of Model Catalysts on Planar Supports

The growing interest in physically deposited model catalysts for uncovering complex structure-activity relationships is spurred by the possibility of depositing nanoparticles of precise atomic structure and composition using cluster-beam sources. However, the limitations accompanying these synthesis techniques, such as low deposition rates and flat sample geometry, present a challenge for in situ structural characterization using bulk-sensitive methods, such as X-ray absorption spectroscopy (XAS), especially at elevated pressures (1-100 bar). To overcome this challenge, we constructed an in situ XAS cell operating in a grazing incidence (GI) geometry. The GIXAS cell was used to investigate the structure of cluster-beam-generated Pd and Au0.3Ag0.7 nanoparticles under CO2-to-methanol hydrogenation conditions (230 degrees C, 20 bar, CO2:H-2=1 : 3). These nanoparticles, with metal loading of 0.96-10 mu g cm(-2), demonstrated stability and resistance to sintering upon activation in H-2 at 120 degrees C and catalytic conditions, revealed by in situ XAS. The promising results from our work will help bridge the gap in the investigation of model catalytic materials produced by gas-phase cluster deposition at industrially relevant pressures and temperatures, which is vital for a mechanistic understanding of catalytic processes.