CARBON-MONOXIDE OXIDATION ON A PT(111) ELECTRODE STUDIED BY IN-SITU IRAS AND STM - COADSORPTION OF CO WITH WATER ON PT(111)

Coadsorption of carbon monoxide (GO) with water on Pt(lll) was investi gated by cyclic voltammogram (CV), in-situ and non-situ IRAS and STM i n order to explore the mechanism of the oxidation of CO to CO, on the surface. CO adsorbed on a Pt(lll) electrode al 0.4 V (RHE) showed a st rong interaction with overlayer water molecules and retarded the oxida tion of CO to CO,, whereas CO adsorbed at 0.05 V started to oxidize at a lower potential. The structure change from (2 x 2)-3CO (theta(CO)=0 .75) to (root 19 x root 19)R23.4-13CO (theta(CO)=0.685) was followed b y an adsorption of water, which played an important role in CO oxidati on. Under UHV a c(4 x 2) structure (theta(CO)=0.50) was observed in pr eference to the compression structures because of the absence of the c oadsorbed water molecule.