Single Alloy Nanoparticle X-Ray Imaging during a Catalytic Reaction

TL;DR

This study uses advanced x-ray imaging to observe the surface strain and composition changes of a single PtRh alloy nanoparticle during catalytic reactions, revealing facet-dependent behavior crucial for catalyst design.

Contribution

First to combine coherent x-ray diffraction imaging with DFT calculations for facet-resolved, operando analysis of alloy nanoparticle catalysts.

Findings

Pt surface becomes Rh enriched under CO oxidation

Rh enrichment varies with facet orientation

Rh enrichment is non-reversible under CO reduction

Abstract

The imaging of active nanoparticles represents a milestone in decoding heterogeneous catalysts dynamics. We report the facet resolved, surface strain state of a single PtRh alloy nanoparticle on SrTiO3 determined by coherent x-ray diffraction imaging under catalytic reaction conditions. Density functional theory calculations allow us to correlate the facet surface strain state to its reaction environment dependent chemical composition. We find that the initially Pt terminated nanoparticle surface gets Rh enriched under CO oxidation reaction conditions. The local composition is facet orientation dependent and the Rh enrichment is non-reversible under subsequent CO reduction. Tracking facet resolved strain and composition under operando conditions is crucial for a rational design of more efficient heterogeneous catalysts with tailored activity, selectivity and lifetime.