The CO-induced lifting of the pseudo-hexagonal, clean surface reconstruction of Pt{100} was re-investigated with infrared reflection-absorption spectroscopy and low-energy electron diffraction. In order to remove inconsistencies arising from previous studies, adsorption on both the reconstructed and the metastable unreconstructed surfaces was studied at 90 to 300K. A sequence of ordered overlayers observed for coverages of 0.5 and above on the unreconstructed surface, including a previously unobserved c(5√2 x √2)R45° structure at a coverage of 0.6, could be interpreted in terms of new structural models involving both atop and bridging CO. During adsorption on the reconstructed surface at 300K the (hex) ↔ (1 x 1) phase transition could be monitored by using the C-O stretch. In particular, the co-existence of CO adsorbed on (hex) and (1 x 1) regions in a narrow coverage range was observed. The appearance of CO on the (1 x 1) phase was not only accompanied by a small shift in the linear C-O stretch, but also by the development of a bridge band. However, at below ≈250K, the reconstruction was lifted in a significantly different way.

The Adsorbate-Induced Removal of the Pt{100} Surface Reconstruction II - CO. R.Martin, P.Gardner, A.M.Bradshaw: Surface Science, 1995, 342[1-3], 69-84