Kinetic study of CO oxidation on copper modified Pt(111)

Abstract

The kinetics of CO oxidation on Pt(111) modified with submonolayer copper adlayers were studied using mass spectrometry (MS) and photoemission electron microscopy (PEEM). The submonolayer 2D copper adlayers were formed on approximately half of the Pt(111) crystal, by evaporating copper through a mask. More precisely, the article deals with the modifications of the hysteresis in the reaction rate compared to the hysteresis occurring under certain reaction conditions on pure Pt(111) when the CO pressure is cyclically varied. When copper was evaporated onto the Pt crystal, the kinetic phase transition between the high and low rate regimes shifted to higher CO pressures and the reaction rate increased. In addition, the CO pressure range in which bistability was observed became wider. Upon increasing the copper coverage, the shift showed a maximum at a coverage of 0.3 ML until at 0.7 ML no clear first-order transition in the reaction rate could be observed any more. The results suggest that the active site responsible for the increased activity lies at the copper–platinum bimetallic border sites.