Reaction-Driven Restructuring of Rh-Pd and Pt-Pd Core-Shell Nanoparticles

TLDR

Bimetallic nanoparticle catalysts can segregate under oxidizing or reducing conditions. Core‑shell Rh(0.5)Pd(0.5) and Pt(0.5)Pd(0.5) nanoparticles were examined in situ by near‑ambient pressure X‑ray photoelectron spectroscopy during oxidizing, reducing, and NO/O₂/CO/H₂ catalytic reactions. Rh(0.5)Pd(0.5) nanoparticles undergo dramatic, reversible compositional changes under oxidizing or reducing conditions, whereas Pt(0.5)Pd(0.5) nanoparticles remain stable, demonstrating the tunable restructuring of bimetallic catalysts during reactions.

Abstract

Heterogeneous catalysts that contain bimetallic nanoparticles may undergo segregation of the metals, driven by oxidizing and reducing environments. The structure and composition of core-shell Rh(0.5)Pd(0.5) and Pt(0.5)Pd(0.5) nanoparticle catalysts were studied in situ, during oxidizing, reducing, and catalytic reactions involving NO, O2, CO, and H2 by x-ray photoelectron spectroscopy at near-ambient pressure. The Rh(0.5)Pd(0.5) nanoparticles underwent dramatic and reversible changes in composition and chemical state in response to oxidizing or reducing conditions. In contrast, no substantial segregation of Pd or Pt atoms was found in Pt(0.5)Pd(0.5) nanoparticles. The different behaviors in restructuring and chemical response of Rh(0.5)Pd(0.5) and Pt(0.5)Pd(0.5) nanoparticle catalysts under the same reaction conditions illustrates the flexibility and tunability of the structure of bimetallic nanoparticle catalysts during catalytic reactions.