Combining high-energy X-ray diffraction with Surface Optical Reflectance and Planar Laser Induced Fluorescence for...

Area of Science:

• Catalysis Science
• Surface Science
• Materials Science

Background:

• Understanding catalytic processes at the molecular level is crucial for developing efficient industrial catalysts.
• Operando studies, which monitor catalysts under reaction conditions, provide critical insights into dynamic surface changes.
• Previous research indicated that Pd(100) surfaces exhibit high activity during CO oxidation before oxide formation is detected.

Purpose of the Study:

• To combine High Energy Surface X-Ray Diffraction (HESXRD), Surface Optical Reflectance, and Planar Laser Induced Fluorescence for operando studies.
• To investigate the CO oxidation reaction over a Pd(100) catalyst.
• To correlate surface structure and morphology changes with catalytic activity at high temporal resolution.

Main Methods:

• Utilized a multi-technique approach including High Energy Surface X-Ray Diffraction (HESXRD), Surface Optical Reflectance, and Planar Laser Induced Fluorescence.
• Performed operando studies to observe catalyst behavior under actual reaction conditions.
• Ensured the probed region was representative of the entire sample surface.

Main Results:

• Confirmed that the Pd(100) surface achieves high catalytic activity prior to detectable oxide formation.
• Demonstrated the capability of the combined techniques to verify the representativeness of probed surface regions.
• Observed and correlated changes in gas composition and surface structure/morphology with catalytic performance at high temporal resolution.
• Revealed that the Pd(100) catalyst surface does not exhibit homogeneous behavior during CO oxidation.

Conclusions:

• The combination of HESXRD, optical reflectance, and laser fluorescence offers valuable insights into operando catalysis.
• Surface heterogeneity in Pd(100) catalysts under mass-transfer-limited conditions is likely due to inhomogeneous gas exposure.
• This integrated approach is effective for studying dynamic changes in catalytic systems.