The interplay of structure, activity and stability - A case study on AgPt/Pt(111) surface alloys

Abstract

In the present thesis structurally well-defined bimetallic model electrodes consisting of AgPt/Pt(111) surface alloys were systematically investigated with a newly developed combination of UHV-STM and electro-catalytic/-chemical studies in an electrochemical flow cell set-up. First, their electrochemical properties and their stability and restructuring upon exposure to an electrochemical environment were analysed, based on a systematic evaluation of bimetallic monolayer surface alloys with increasing Ag surface content. Second, the ORR activities of the bimetallic surface electrodes were studied and correlated with the exact atomic distribution of the surface, including comparison with a kinetic model based on a Sabatier-type analysis. Third, the stability and corrosion of AgPt/Pt(111) surface alloys in dependence on the upper potential limit in electrochemical experiments was characterized. The results of these studies clearly demonstrate the extent and level of detail of information and mechanistic insights gained on the corrosive modification of bimetallic surfaces, which are a precondition for deriving structure-activity relationships. Furthermore, they show the level of measurement accuracy, which is necessary for the interpretation of the electrocatalytic properties of (bimetallic) electrodes for ORR studies.