Adsorption of CO on Pt(111) and Pt 6(111) × (111) studied by high resolution electron energy loss spectroscopy and thermal desorption spectroscopy

Abstract

The adsorption of CO on the smooth (111) and stepped 6(111) × (111) surface of platinum has been studied by high resolution electron energy loss spectroscopy (ELS) and thermal desorption spectroscopy (TDS). TDS yields only one desorption peak for the (111) surface while for the stepped surface a second peak with higher temperatures occurs. ELS shows that CO is adsorbed molecularly on either surface. On the (111) surface two adsorption sites are occupied, namely on top and bridge sites which are filled subsequently. A correlation with LEED structures at 150 K shows that in the 3 × 3 R30° structure only on top sites are occupied and for the c(4 × 2) structure also bridge sites are involved. ELS for the stepped surface shows additional peaks which are attributed to CO adsorbed at step sites. Two different step sites are proposed. The occurrence of small peaks with a very low CO stretch frequency are believed to be due to adsorption at structural defects (kinks) of the stepped surface.