1998 Alcan Award Lecture Surface electrochemistry - surface science with a joy stick

Abstract

This lecture gives a review of thermodynamic, spectroscopic, STM and AFM imaging, and X-ray diffraction studies of molecular and ionic adsorption at Au(111) electrodes. In the first part, thermodynamics of adsorption of simple ions such as sulfate, chloride, bromide, and iodide will be discussed. At high coverages, anions adsorbed at a single crystal surface form ordered 2D adlayers. We show that the structure of these adlayers can be studied by STM and surface X-ray diffraction techniques. Next, the information concerning adsorption of simple ions is used to describe mixed adlayers formed by coadsorption of anions and metal adatoms. We demonstrate how to combine electrochemical experiments with in situ polarization-dependent Cu K-edge X-ray absorption spectroscopy to determine the composition and the structure of mixed films formed by deposition of Cu on Au(111) in the presence of SO42-. In the last part we review our efforts to describe coordination of organic molecules to gold electrodes. First, we will discuss adsorption of benzonitrile at the Au(111) electrode surface. We combine electrochemical methods with in situ infrared spectroscopy to describe (i) the energetics of molecular adsorption at the gold electrode surface, (ii) the character of the interaction of the adsorbed molecule with the metal substrate, and (iii) the influence of the electric field on the orientation of the adsorbed molecule. In the last section we describe surface aggregation phenomena. We apply AFM and STM to determine the structure of hemimicelles formed at the Au(111) electrode surface by adsorbed molecules of sodium dodecyl sulfate and we discuss the potential-controlled transformation of these hemimicelles into a condensed monolayer.Key words: surface electrochemistry, electrosorption, surface aggregation, gold electrodes, molecular adsorption, ionic adsorption.