Bremen-Cardiff Physics Seminar
Oxide formation at Pt-Sn model catalyst surfaces
Speaker: Prof. Lindsay Richard Merte (Univesity of Malmö, Sweden)
Date: Tuesday 22 June 2021
Time: 14:00 in UK
Venue: Zoom
Tin has been exploited as a promoter of platinum catalysts for decades, particularly for application in naphtha reforming and in direct-alcohol fuel cells. Pt-Sn electrocatalysts show high activities for oxidation reactions and high tolerance against CO poisoning. However, the bimetallic system is complex and dynamic, with tin potentially present in alloyed form, as 2+ or 4+ oxides, or mixtures of these, and catalytic reactions can take place on any of these phases or at the interfaces between them. Facile oxidation and reduction processes furthermore enable transformations between these phases under reaction conditions. Fundamental studies are needed to disentangle these effects, to resolve the structures of the active sites for reactions on these catalysts and the factors that govern their formation and properties.
I will present our recent investigations of the behavior of Pt3Sn(111) single crystals, which serve as simplified models for Pt-Sn catalysts. Our main focus so far has been on the oxidation of Pt3Sn(111) surfaces and on the structures and properties of the oxides that are formed. A first step toward understanding this complex system has been the determination of the structure of a 2D SnOx wetting layer on the Pt3Sn(111) surface, which has been achieved by application of large-scale DFT-and machine-learning-based global optimization, together with scanning probe microscopy and surface X-ray diffraction. In situ studies at high vacuum and millibar pressures of CO and O2 reveal the formation and transformations of these and related tin oxide wetting layers, and provide insight into the behavior of the complex material system under reaction conditions.