The electronic structure and orientation of styrene adsorbed on FeO(111) and Fe3O4(111) - A spectroscopic investigation

The adsorption of styrene on (111)-oriented thin layers of FeO and Fe3O4 epitaxially grown on Pt(111) single-crystal surfaces has been investigated using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). High-resolution gas-phase measurements were recorded, and precise ab initio electronic structure calculations were performed in order to aid the assignment of the NEXAFS resonances. Whereas on Fe3O4 (magnetite), styrene forms a chemisorbed monolayer that is stable up to room temperature, on FeO (wustite), a significantly more weakly bound (physisorbed) species is observed that is stable only for temperatures below 200 K. A planar adsorption geometry is observed in the case of styrene on Fe3O4 in the low-coverage regime (ϑ < 0.5 ML); for higher coverages on the same surface and on FeO, the average tilt angle between the phenyl plane and the surface plane amounts to about 45°.