Infrared Reflection−Absorption Study of Carbon Monoxide Adsorption on Fe/Pt(111) Bimetallic Surfaces

Infrared reflection−absorption spectroscopy (IRRAS) was used to investigate carbon monoxide (CO) adsorption on sub-monolayer (ML)-thick to 1.0 ML-thick Fe deposited Pt(111) bimetallic surfaces, that is, Fex/Pt(111) (x, Fe thickness in ML units), fabricated using molecular beam epitaxy at substrate temperatures of 343, 403, and 473 K. The 1.0 L CO exposure to a clean Pt(111) at room temperature yielded linearly bonded and bridge-bonded CO−Pt bands at 2093 and 1855 cm−1. The CO−Pt band intensities for the CO-exposed surfaces of the Fex/Pt(111) decreased with increasing Fe thickness. The CO−Pt bands almost disappeared, and the bridge-bonded CO−Fe band at 1950 cm−1 dominated the spectra for the Fe1.0ML/Pt(111) deposited at 343 K. In addition, the Fe deposition brought about a new absorption band at around 2060 cm−1; this band is predominant for the Fe0.5ML/Pt(111) deposited at 473 K. The 1 ML-thick Fe deposition onto the 473 K Pt(111) engenders less-intense, rather broad absorption at 2050 cm−1, accompanied b...