Adsorption and interaction of CO and NO on Pt(410): II. Infrared studies

Abstract

The adsorption of CO and NO on Pt(410) is studied with single reflection infrared spectroscopy (IR). Adsorption of CO on Pt(410) gives a single IR band which shifts from 2072 to 2090 cm −1 with increasing exposure. This shift can be decomposed into a 36 cm −1upward shift due to dipole interactions between adjacent CO molecules on the surface, and an 18 cm −1 downward shift due to a change in the chemical environment on the surface as lower binding states fill. This produces a change in the singleton frequency with coverage. There is no evidence for CO island formation on this surface. There is also no evidence for “bridge bound” CO on a clean Pt(410) surface at 300 K. However, a “bridge bound” peak is observed at 1869 cm −1 on a surface that had been contaminated by a small amount of carbon. Adsorption of NO on Pt(410) yields a small IR band at 1638 cm −1 at exposures above 6 L. The peak has a maximum intensity corresponding to less than 6% of a monolayer and disappears when the surface is heated to 340 K. Experiments with a contaminated surface indicated that the molecular NO might be associated with silicon contaminated regions on the surface. The CO/NO reaction on Pt(410) is also discussed.