Gas-Induced Segregation in Pt-Rh Alloy Nanoparticles Observed by In Situ Bragg Coherent Diffraction Imaging

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis

Background:

• Bimetallic catalysts are crucial for various chemical reactions.
• Their performance is sensitive to the distribution of constituent metals.
• Oxidizing and reducing environments can induce metal segregation in nanoparticles.

Purpose of the Study:

• To investigate the dynamic compositional changes in bimetallic nanoparticles under varying gas conditions.
• To correlate structural and compositional changes at the nanoscale.
• To demonstrate the utility of Bragg coherent diffraction imaging (BCDI) for in situ analysis.

Main Methods:

• Utilized Bragg coherent diffraction imaging (BCDI) to achieve high-resolution 3D imaging.
• Analyzed crystalline platinum-rhodium (Pt-Rh) alloy nanoparticles.
• Changed the surrounding gas environment between oxygen (O2) and hydrogen (H2) to observe dynamic changes.

Main Results:

• Observed partial reversal of radial compositional distribution between the nanoparticle core and surface shell upon switching gas environments.
• Successfully related displacement fields to internal compositional distributions.
• Provided 3D images of the internal composition of Pt-Rh nanoparticles.

Conclusions:

• Elemental segregation in nanoparticle catalysts is highly active during heterogeneous catalysis.
• Dynamic compositional changes can be a controlling factor in the synthesis of electrocatalysts.
• BCDI is a powerful technique for in situ 3D imaging of internal compositions in bimetallic alloy nanoparticles.