Initial stages of palladium deposition on Au(h k l): Part III: Pd on Au(1 1 0)

The deposition of palladium onto the unreconstructed Au(1 1 0) surface was studied by cyclic voltammetry and in situ scanning tunnelling microscopy. An ordered adlayer of [PdCl4]2− was imaged with atomic resolution on the bare Au(1 1 0) surface. Pd deposition starts at monoatomic high steps by forming a layer that grows onto the lower terrace. Coulometric data point towards the deposition of approximately three monolayer equivalents in the Pd underpotential region. This high coverage and the presence of holes in the Au(1 1 0) surface after the complete anodic dissolution of the Pd deposit are explained by surface alloy formation. Furthermore, the palladium overlayers on Au(1 1 0) appear to be rather rough, because there is no strict layer-by-layer growth. Important aspects of the initial stages of palladium deposition on the three low-index Au surfaces are summarised and the influence of the crystallographic orientation of the substrate as well as the effect of different Pd film thicknesses on the electrochemical properties are briefly discussed.