Gas-induced segregation in Pt-Rh alloy nanoparticles observed by in-situ Bragg coherent diffraction imaging

TL;DR

This study uses Bragg coherent diffraction imaging to observe how gas environments induce segregation in Pt-Rh alloy nanoparticles, revealing dynamic compositional changes relevant for catalysis and synthesis.

Contribution

It demonstrates the application of in-situ 3D BCDI imaging to visualize internal compositional redistribution in bimetallic nanoparticles under different gas conditions.

Findings

Radial composition distribution reverses between surface and core with gas changes

Segregation is highly active during catalysis

BCDI enables in situ 3D imaging of alloy nanoparticles

Abstract

Bimetallic catalysts can undergo segregation or redistribution of the metals driven by oxidizing and reducing environments. Bragg coherent diffraction imaging (BCDI) was used to relate displacement fields to compositional distributions in crystalline Pt-Rh alloy nanoparticles. 3D images of internal composition showed that the radial distribution of compositions reverses partially between the surface shell and the core when gas flow changes between O2 and H2. Our observation suggests that the elemental segregation of nanoparticle catalysts should be highly active during heterogeneous catalysis and can be a controlling factor in synthesis of electrocatalysts. In addition, our study exemplifies applications of BCDI for in situ 3D imaging of internal equilibrium compositions in other bimetallic alloy nanoparticles.