Anion adsorption and atomic friction on Au(1 1 1)

The influence of anion adsorption on friction forces in an electrochemical environment has been studied by means of lateral force microscopy on Au(1 1 1) surfaces. Sensitivity to atomic stick-slip motion allows to reveal sulphate adsorption in ordered layers under the sliding tip at potentials lower than expected from cyclic voltammetry for the open surface. No ordered adsorption is found in lateral force measurements for the weakly adsorbed perchlorate anions. Correspondingly, some increase in friction in the anion adsorption regime is observed for sulphate but none for perchlorate adsorption. Friction increases significantly at the onset of oxidation in both sulphuric and perchloric acid solutions.

► Electrochemical lateral force microscopy on Au(1 1 1) in sulphuric and perchloric acid.
► Lateral forces at the atomic scale are sensitive to the adsorption state of anions.
► Friction changes at lower potentials than expected from cyclic voltammograms.
► Friction increases with normal load when sliding on specifically adsorbed anions.
► A dramatic increase in friction occurs upon electrochemical oxidation of the surface.