Origins of the High Reactivity of Au Nanostructures Deduced from the Structure and Properties of Model Surfaces

Abstract

In this chapter, experimental and theoretical studies on surface segregation in Ag-Au systems, including our own thermodynamic studies and molecular dynamics simulations of surface restructuring, on the basis of density functional theory are reviewed. The restructuring processes are triggered by adsorbed atomic O, which is supplied and consumed during catalysis. Experimental evidence points to the essential role of Ag impuri- ties in nanoporous gold for activating O 2 . At the same time, increasing Ag concentration may be detrimental for the selectivity of partial oxidation. Understanding the role of silver requires a knowledge on its chemical state and distribution in the material. Recent studies using electron microscopy and photoelectron spectroscopy shed new light on this issue revealing a non-uniform distribution of residual Ag and co-existence of different chemical forms of Ag. We conclude by presenting an outlook on electromechanical coupling at Ag- Au surfaces, which shows a way to systematically tune the catalytic activity of bimetallic surfaces.