The adsorption of CO on Pt{110} over the temperature range from 90 to 300 K studied by RAIRS

We have performed a thorough infrared study of the adsorption of CO over the temperature range from 90 to 300 K. CO occupies on-top sites exclusively at all coverages and temperatures. No C-O frequency change is seen when the (1 x 2) reconstructed surface phase converts to the (1 x I) surface phase. At 300 K, the on-top CO molecules are bonded to the top layer of Pt atoms only. At 90 K. the observed saturation coverage on the frozen-in (I x 2) surface is the same as that at 300 K and hence on-top sites on second layer Pt atoms must also be occupied. Heating: the saturated adlayer formed at 90 K to 140-160 K leads to a marked intensity increase in the CO band, which is assigned to the creation of a c(8 x 4) surface phase; Further heating above 250 K completely converts the Pt surface to the (1 x 1) phase. The driving force for the restructuring process is the increase in heat of adsorption for on-top CO on top row atoms compared with second layer Pt atoms which must exceed the energy difference between the two clean surface phases. (C) 1998 Elsevier Science B.V. All rights reserved.