Single alloy nanoparticle x-ray imaging during a catalytic reaction

Area of Science:

• Surface science
• Materials science
• Catalysis

Background:

• Understanding nanoparticle dynamics is key to advancing heterogeneous catalysis.
• Active nanoparticle imaging provides insights into catalyst behavior under reaction conditions.

Purpose of the Study:

• To investigate the facet-resolved surface strain and composition of a single platinum-rhodium (PtRh) alloy nanoparticle.
• To correlate surface strain with chemical composition under operando catalytic conditions.

Main Methods:

• Coherent X-ray diffraction imaging was used to determine the facet-resolved surface strain state of a single PtRh nanoparticle on strontium titanate (SrTiO3).
• Density functional theory (DFT) calculations were employed to link surface strain to reaction environment-dependent chemical composition.

Main Results:

• The study revealed the facet-resolved surface strain state of a single PtRh alloy nanoparticle under catalytic reaction conditions.
• PtRh nanoparticles initially terminated with platinum (Pt) showed enrichment with rhodium (Rh) under carbon monoxide (CO) oxidation conditions.
• The observed Rh enrichment was facet orientation dependent and irreversible under subsequent CO reduction.

Conclusions:

• Tracking facet-resolved strain and composition under operando conditions is essential for designing efficient heterogeneous catalysts.
• Tailoring catalyst activity, selectivity, and lifetime requires a detailed understanding of dynamic surface changes.
• The findings highlight the importance of considering dynamic compositional changes in catalyst design.