Formation and Segregation of a Pd-MgO Solid Solution Studied by X-ray Absorption Spectroscopy

Kazu Okumura; Sachiko Morita; Hikaru Iiyoshi; Hiromitsu Takaba

doi:10.1021/acsomega.2c06604

Formation and Segregation of a Pd-MgO Solid Solution Studied by X-ray Absorption Spectroscopy

ACS Omega. 2023 Feb 16;8(8):7507-7516. doi: 10.1021/acsomega.2c06604. eCollection 2023 Feb 28.

Authors

Kazu Okumura¹, Sachiko Morita¹, Hikaru Iiyoshi¹, Hiromitsu Takaba²

Affiliations

¹ Department of Applied Chemistry, School of Advanced Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji 192-0015, Tokyo, Japan.
² Department of Environmental Chemistry and Chemical Engineering, School of Advanced Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji 192-0015, Tokyo, Japan.

Abstract

Thermal treatment of Pd nanoparticles or Pd(NH₃)₄(NO₃)₂ supported on MgO resulted in the formation of a solid solution of Pd-MgO, as evidenced by Pd K-edge X-ray absorption fine structure (XAFS). The valence of Pd in the Pd-MgO solid solution was determined to be 4+ from the comparison of X-ray absorption near edge structure (XANES) with reference compounds. A characteristic shrinkage of the Pd-O bond distance was observed in comparison with that of the nearest-neighboring Mg-O bond in MgO, which agreed with the density functional theory (DFT) calculations. The two-spike pattern was observed in the dispersion of Pd-MgO owing to the formation and successive segregation of solid solutions above 1073 K.