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

Abstract

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 Au_0.3Ag_0.7 nanoparticles under CO₂-to-methanol hydrogenation conditions (230 °C, 20 bar, CO₂:H₂=1 : 3). These nanoparticles, with metal loading of 0.96–10 μg cm⁻², demonstrated stability and resistance to sintering upon activation in H₂ at 120 °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.