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

Abstract

Valence-band and core x-ray-photoemission spectroscopy has been used to examine the electronic structure of FeOOH and ${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$. The known small difference in the core-level Fe 2p spectra of the two compounds is discussed. X\ensuremath{\alpha} calculations of an ${\mathrm{FeO}}_{6}$${\mathrm{H}}_{3}^{3\mathrm{\ensuremath{-}}}$ 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}$${\mathrm{O}}_{3}$ can be clearly distinguished in the valence-band region. X\ensuremath{\alpha} calculations of an ${\mathrm{FeO}}_{6}^{9\mathrm{\ensuremath{-}}}$ cluster are found to predict the three-peak structure of the ${\mathrm{Fe}}_{2}$${\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 X\ensuremath{\alpha} calculation. Little decomposition of FeOOH is found during data collection.