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

[Image: see text] Thermal treatment of Pd nanoparticles or Pd(NH(3))(4)(NO(3))(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.