A Vibrational Spectroscopic Investigation of No and Co Coadsorption on Pt ( 100 )

The co-adsorption of NO and CO on Pt{100} at 300 K has been investigated using infrared reflection-absorption spectroscopy (IRAS). At low coverages, regardless of the order of adsorption, mixed NO/CO islands are formed on (1 x 1) domains. This causes the stretching modes of both species to shift down in frequency due to reduced dipole-dipole coupling. The lowest frequency of approximately 2050 cm-1 observed for CO fully diluted in NO is only approximately 10 cm-1 less than C-12-O-16 diluted in C-12-O-18, indicating a relatively small chemical interaction. NO/CO mixing is not observed on the (hex) surface at 300 K since NO immediately lifts the reconstruction. In all cases, CO was able to penetrate an NO layer and eventually remove it but a saturated CO layer cannot be penetrated by NO.