Tracking dynamic structural changes in catalysis by rapid 2D-XANES microscopy.

Area of Science:

• Heterogeneous catalysis
• Materials science
• Spectroscopic characterization

Background:

• Catalytic materials undergo dynamic structural changes influenced by their chemical environment.
• Conventional spectroscopic tools struggle to capture these rapid changes due to time resolution limitations.

Purpose of the Study:

• To develop and apply a novel spectro-microscopic imaging technique for monitoring dynamic chemical processes in catalysts.
• To observe chemical gradients and transformations within a model catalyst during a reaction.

Main Methods:

• Synchronization of a high-resolution 2D X-ray camera (50 Hz full-frame rate) with a QEXAFS monochromator.
• Rapid spectro-microscopic imaging with chemical contrast at the pixel level.
• Monitoring chemical gradients in a Pt/Al2O3 catalyst during methane partial oxidation.

Main Results:

• Observed the transition from methane combustion to combustion-reforming and partial oxidation.
• Identified a characteristic reduction front progressing through the catalyst bed on a second timescale.
• Demonstrated the ability to acquire entire X-ray absorption near edge structure (XANES) spectra rapidly and with spatial resolution.

Conclusions:

• The full-field QEXAFS imaging method enables 'on the fly' acquisition of spatially resolved spectroscopic data.
• The combination of high spatial and temporal resolution provides new insights into dynamic processes in catalysts and functional materials.
• The flexible methodology is applicable to various beamlines and catalytic studies.