X-ray photoelectron spectroscopy study of anodically oxidized SIMFUEL surfaces

Abstract

The surface composition of anodically oxidized SIMFUEL (doped uranium dioxide) has been determined as a function of applied potential over the range -500 to +500mV (versus SCE). Cathodically cleaned UO2 specimens were anodically oxidized for 1h and subsequently analyzed by XPS. Using published binding energies, the U (4f7/2) and O (1s) peaks were resolved into contributions from UIV, UV, UVI, O II, OH- and H2O. It was shown that over the potential range -500 to approximately +50mV a thin surface layer of U IV/UV oxide (UO2+x) formed. At more positive potentials, a UVI hydrated oxide (UO3·yH 2O) was deposited on the electrode surface. At very positive potentials (≥400mV) the rapid anodic formation and hydrolysis of UO 22+ led to local acidification in pores in the deposited UO3·yH2O layer and its subsequent re-dissolution. © 2004 Published by Elsevier Ltd.