COMPARATIVE-STUDY OF THE ADSORPTION OF CO, NO AND HYDROGEN ON (1X1) AND (1X2) RH(110)

The adsorption of CO, NO and hydrogen on the (1 x 1) and (1 x 2) Rh(110) surfaces has been studied by means of LEED, TPD and AES at temperatures above 125 K. On the (1 x 2) surface, CO adsorption resulted in c(2 x 4) (for 0.40 < theta < 0.63 ML) and (2 x 2)pg (for theta = 1 ML) LEED patterns while saturation adsorption of NO gave rise to a (1 x 4) pattern. Unlike on the (1 x 1) surface, no H induced LEED patterns were observed on the (1 x 2) surface. The effect of the different structure of the substrate depends strongly on the type of molecule. In particular, H is substantially more strongly adsorbed on the (1 x 2) surface, while NO partly desorbs and partly dissociates on both surfaces, but a larger fraction desorbs molecularly from the (1 x 2) surface. CO is only slightly more strongly bound on the (1 x 1) surface. The different adsorption states are described and tentative models are provided.