Formation of a Pt-MgO Solid Solution: Analysis by X-ray Absorption Fine Structure Spectroscopy

Thermal treatment of Pt nanoparticles or Pt(acac)₂ supported on MgO resulted in the formation of a solid solution of Pt-MgO, as evidenced by Pt L₃-edge X-ray absorption fine structure spectroscopy. The valence of Pt in the Pt-MgO solid solution was determined to be 4+. A characteristic shrinkage of the Pt-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 segregation of Pt and MgO proceeded with a further increase in the thermal treatment temperature up to 1273 K. The dispersion of Pt on MgO measured through CO adsorption was much higher than that on Al₂O₃ or SiO₂ owing to the formation of the Pt-MgO solid solution.