Investigation into the Palladium-Europium Acetate Reductive Decomposition with Synchrotron Radiation-Based X-ray Diffraction and X-ray Absorption Spectroscopy

The reductive decomposition of the complex Pd₂Eu₂(μ,η²‐OOCMe)₂(μ‐OOCMe)₈(H₂O)₂·(HOOCMe)₂ upon heating from room temperature to 500 °C in a hydrogen atmosphere was investigated by in situ synchrotron radiation‐based X‐ray absorption fine structure spectroscopy (XAFS) including observations of X‐ray near‐edge structure (XANES) and extended absorption fine structure (EXAFS) at Pd K‐ and Eu L₃‐edges and synchrotron X‐ray diffraction (XRD). The Pd‐Eu₂O₃ nanocomposite was found to be the final thermolysis product. The decomposition proceeds via series of intermediate crystalline phases, including europium(II) and (III) anhydrous acetates and EuO(CH₃COO) oxidoacetate. Surprisingly, the major fraction of europium occurs in the reduced form Eu²⁺ within a limited temperature range of 200–300 °C. Presumably, the reversible Eu³⁺↔Eu²⁺ redox‐process is associated with the stability of nanocrystalline palladium hydride, which acts as a stronger reducing agent as compared to molecular hydrogen.