Insight into restructuring of Pd-Au nanoparticles using EXAFS. (October 2020)

• Record Type: Journal Article
• Authors: Boubnov, Alexey; Timoshenko, Janis; Wrasman, Cody J.; Hoffman, Adam S.; Cargnello, Matteo; Frenkel, Anatoly I.; Bare, Simon R.
• Is Part Of: Radiation physics and chemistry. Volume 175(2020:Oct.)
• Publication Date: 2020-10
• Subjects: Dilute alloy -- Palladium -- Gold -- Catalyst -- Multi-edge EXAFS -- Structural model; Radiation chemistry -- Periodicals; Radiometry -- Periodicals; Radiation -- Periodicals; Chimie sous rayonnement -- Périodiques; 539.2
• DOI: 10.1016/j.radphyschem.2019.04.054
• Languages: English
• ISSNs: 0969-806X

Abstract

Abstract: We acquired Pd K-edge and Au L3 -edge EXAFS spectra of two libraries of titania-supported Pd-doped Au nanoparticle catalysts representing the as-prepared and post-catalysis state. The nanoparticles have narrow particle size distributions, in the range 2.8–6.6 nm, and were synthesized to preferentially locate the palladium atoms on the surface of a gold core, with Pd mole fractions of 1.4–38%. EXAFS spectra of both the as-prepared samples and post-catalysis Pd-Au particles were collected and modeled. EXAFS refinement of all samples showed contributions from both Pd-Au and Pd-Pd scattering paths, revealing that Pd and Au components alloyed together. Pd was in a partially oxidized state as evidenced by a Pd-O scattering contribution, unlike Au. Overlaying measured coordination numbers from the libraries with predicted values, using models of surface and bulk alloying, showed that Pd restructures among Au as a result of exposure to the reaction conditions. Highlights: Data collected by two groups from two different synchrotrons. Structural model developed for predicting coordination numbers for surface and bulk alloying. Detailed modeling of EXAFS data from a library of Pd-doped Au nanoparticles. Insight gained on the alloying as function particle size and composition.