Photoemission and electronic structure of FeOOH: Distinguishing between oxide and oxyhydroxide

Valence-band and core x-ray-photoemission spectroscopy has been used to examine the electronic structure of FeOOH and ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$. The known small difference in the core-level Fe 2p spectra of the two compounds is discussed. Xα calculations of an ${\mathrm{FeO}}_6$ ${\mathrm{H}}_3^{3\mathrm{-}}$ cluster are shown to give good agreement with the two-peak FeOOH valence-band XPS spectrum, and it is clear that FeOOH and ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ can be clearly distinguished in the valence-band region. Xα calculations of an ${\mathrm{FeO}}_6^{9\mathrm{-}}$ cluster are found to predict the three-peak structure of the ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ valence band. The O 2s region of FeOOH is found to be more sensitive to chemical environment than the O 1s region, and the former region is well explained by the Xα calculation. Little decomposition of FeOOH is found during data collection.