On the chemisorption of oxygen on platinum (111) surfaces

Chemisorption of oxygen on clean platinum (111) surfaces at room temperature can be readily observed by the development of a (2×2) −O LEED pattern provided the carbon monoxide content of the residual gas is less than 0.5%. The (2×2) −O pattern disappears during reevacuation of the surface research system, indicating that a critical ratio of pO2/pCO is required for the formation of an adsorbed layer of oxygen. These results suggest that similar ’’clean−off’’ reactions occur in the platinum/oxygen chemisorption system as were observed recently by other researchers for the silver−oxygen and copper−oxygen systems. These results may also explain the failure to observe the chemisorption of oxygen on low index surfaces of platinum in vacuum systems which have been extensively used for studies of carbonaceous gases.