The transient behaviour of Pt-Rh(410) alloy surfaces upon interaction with O 2, No and CO

Abstract

The influence of the initial surface composition of Pt-Rh alloy (410) single crystal surfaces on their reactivity towards O 2, NO and CO has been investigated using AES, XPS and thermal reaction mass spectroscopy (TRMS). The initial surface composition was varied by a proper choice of the equilibration temperature in vacuum. The results show that the Rh-rich surfaces are more active in NO bond breaking than the Pt-rich ones. However, the maximum CO 2 production for the reactions of CO with O 2 or NO occurs at a temperature ( T m), where NO dissociation is already complete on both Rh- and Pt-rich surfaces. It appears that T m depends on the metal-oxygen bond strength and on the CO O 2 or CO NO molar ratio in the reaction mixture, indicating that CO 2 is produced by the reaction of CO(ads) and O(ads). Under reaction conditions both thermal effects and chemisorption can alter the surface composition and, hence, the reactivity of the Pt-Rh(410) surfaces.