Oxidation‐State Analysis of Ceria by X‐ray Photoelectron Spectroscopy

Three different methods to determine the oxide‐phase concentration in mixed cerium oxide by hard X‐ray photoelectron spectroscopy are applied and quantitatively compared. Synchrotron‐based characterization of the O 1s region was used as a benchmark to introduce a method based on the weighted superposition of the Ce 3d spectra of the pure Ce³⁺ and Ce⁴⁺ phases, which was shown to lead to reliable and highly accurate determination of the mean oxidation state in mixed cerium oxides. The results obtained reveal a linear relation between the third distinct final state (u′′′) satellite peak intensity of the Ce⁴⁺ phase and the Ce⁴⁺ concentration by proper inclusion of Ce³⁺‐related plasmon satellite peaks, which contradicts previous claims of nonlinear behavior. In contrast, quantitative conventional peak‐fitting procedures were shown to be well suited for the Ce 2p region due to its relatively simple structure. Additional satellite features observed in the Ce 3d spectrum of CeO₂ were proposed to originate from plasmon contributions.