LAUSR

Abstract Au-based materials are remarkably efficient catalysts in the domain of partial oxidation reactions. Nonetheless, questions remain about the physico-chemical phenomena involved at the molecular level. In this work, the catalytic properties of Au-Ag samples, in the form of ultrathin Ag layers on a Au(1 1 1) surface and Au-based model nanoparticles, have been investigated with different microscopy techniques. Using photoemission electron microscopy (PEEM), the exposure of a Au(1 1 1) single crystal doped with various amounts of Ag (0 to 3 monolayers) to O2/H2 and O2/CH3OH gas mixtures did not lead to any specific spatiotemporal pattern formation. In contrast, the use of curved nanoscopic Au and Au-8.8 at.% Ag tip-samples analysed by field emission microscopy (FEM) under similar experimental conditions indicates the presence of catalytic activity. The influence of the silver concentration and of the morphology on the reactivity is discussed. This work highlights the necessity of different experimental approaches aimed at bridging the materials gap often encountered between surface science studies and applied catalysis.