PNNL

Abstract

The chemistry of methanol on the R-cut surface of hematite was studied in ultrahigh vacuum (UHV) using temperature programmed desorption (TPD), and electron energy loss spectroscopy in both the electronic (EELS) and vibrational ('high resolution' - HREELS) regimes. The R-cut hematite surface, also referred to as the alpha-Fe2O3(012) surface has two stable surface structure in UHV. The (1x1) surface is obtained after oxidation with O2 at 750K, and has a bulk terminated structure possessing undercoordinated Fe3+ and O2- surface sites. The phonon and electronic spectra of this surface are consistent with those of hematite. In contrast, the (2x1) reconstructed surface, obtained by annealing the (1x1) surface at 950 K, possesses Fe2+ surface sites based on the electronic spectrum, but is essential hematite in structure based on the phonon spectrum. Although the atomic arrangements of the (2x1) surface are not known, the reconstruction modifies every other row of cation and anion sites that run parallel to the surface along the [1 2 1] direction.