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Formation and Segregation of a Pd-MgO Solid Solution Studied by X-ray Absorption Spectroscopy
Kazu Okumura1, Sachiko Morita1, Hikaru Iiyoshi1
1Department of Applied Chemistry, School of Advanced Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji 192-0015, Tokyo, Japan.
ACS Omega
|March 6, 2023
Summary
Thermal treatment of palladium (Pd) nanoparticles on MgO forms a Pd-MgO solid solution. This palladium-magnesium oxide solid solution exhibits Pd in a 4+ valence state and structural changes, confirmed by X-ray absorption fine structure (XAFS) and density functional theory (DFT) calculations.
Area of Science:
- Materials Science
- Nanotechnology
- Catalysis
Background:
- Palladium nanoparticles are crucial in catalysis.
- Understanding the interaction between metal nanoparticles and supports is key for catalyst design.
- Magnesium oxide (MgO) is a common catalyst support material.
Purpose of the Study:
- To investigate the formation and properties of palladium-magnesium oxide (Pd-MgO) solid solutions.
- To characterize the valence state and structural characteristics of Pd within the Pd-MgO solid solution.
- To explore the thermal stability and segregation behavior of Pd-MgO solid solutions.
Main Methods:
- Thermal treatment of palladium nanoparticles and palladium precursors on MgO.
- Pd K-edge X-ray absorption fine structure (XAFS) analysis.
- X-ray absorption near edge structure (XANES) spectroscopy with reference compounds.
- Density functional theory (DFT) calculations.
Main Results:
- Formation of a Pd-MgO solid solution was confirmed by XAFS.
- Palladium in the solid solution was identified to be in a 4+ valence state.
- A reduced Pd-O bond distance was observed, consistent with DFT calculations.
- A two-spike pattern in Pd-MgO dispersion indicated solid solution formation and segregation above 1073 K.
Conclusions:
- Thermal treatment leads to the formation of a stable Pd-MgO solid solution.
- The Pd-MgO solid solution exhibits unique structural and electronic properties.
- The findings provide insights into metal-support interactions and high-temperature catalyst behavior.
