X-ray Absorption Spectroscopy of Small Chromium Oxide Particles (Cr₂O₃, CrO₂) Supported on Titanium Dioxide

The oxygen 1s X-ray absorption near-edge structure spectra were obtained for chromium(III) oxide, Cr2O3, and chromium(IV) dioxide, CrO2, supported on titania, TiO2, as well as for the bulk crystalline materials and, for comparison, for a chromium(VI) compound K2Cr2O7. The spectra exhibit a sharp split White line (WL) at about 533.5 eV near threshold. This structure can be explained in terms of ligand-field and exchange splitting. A peak (shoulder) due to the O(1s) → O(2p)Cr(3d) (spin-up t2g) transition could only be observed in the spectra of CrO2. The shape of the WL depends strongly on the oxidation state of the chromium ions in the probed samples suggesting that the WL can be used as an indicator of different environments in the supported chromium oxide films