Surface core-level shifts for Pt single-crystal surfaces

The (111) and (110) surfaces of Pt, clean, oxidized, and covered by CO, have been investigated for surface $4f$ core-level binding-energy shifts. For the (111) face the surface Pt4f7/2 core level was shifted by 0.40±{}0.05 eV to lower binding energy relative to the bulk peak. On the (110)-(1×{}2) reconstructed surface similarly shifted peaks at 0.21±{}0.05 and 0.55±{}0.05 eV were observed. Chemisorbed carbon monoxide shifts the Pt(111) surface-related core level by 1.3 eV to higher binding energy. Formation of subsurface oxygen did not produce changes in the Pt(111)4f7/2 core-level binding energies. The results obtained are explained and their possible implications are discussed.