Surface chemistry of Pu oxides

X-ray photoelectron spectroscopy was used to examine the surface chemistry of a variety of Pu(IV) compounds, including PuO2 and Pu(OH)4. The Pu 4f, O 1s and C 1s binding energy regions were line shape fit to unequivocally demonstrate that multiple species are present. Surface hydroxyls were ubiquitous in all PuO2 samples exposed to H2O vapor or ambient air, and persisted with heating to 590 °C. Active surface sites for the reaction of H2O and other small molecules and spectral features consistent with pure stoichiometric PuO2 can be regenerated by thermal energy or by effects of a radiation field. Evidence of higher valence Pu species was observed in some treated samples with the formula PuO2+x.