Potential-induced stress in the solid-liquid interface: Au(111) and Au(100) in an HClO4 electrolyte

The cantilever bending method is applied to the determination of the potential-induced interface stress for Au(111) and Au(100) in 0.1M HClO4. The bending of the crystal plates was observed using an electrochemical STM. By a reconsideration of the elasticity theory of bending, it is shown that the entire interface including the liquid part contributes to the measured stress. The potential-induced lifting of the reconstruction of the two surfaces was observed using the STM simultaneously with the measurement of the interface stress. By making use of the fact that after cycling the potential between - 140 and 960 mV versus SCE the surfaces remain in an unreconstructed state, one can determine independently the stresses which are associated with the surface reconstruction and with the specific adsorption of ClO4- ions. The stress induced by the specific adsorption is comparable in size to the adsorption-induced stress for surfaces in vacuum. The reconstruction-related changes in the surface stress are discusssed in the context of theoretical models for the reconstruction. The results support the notion that the stress is the driving force for the reconstruction on Au(111), whereas on Au(100) stress relaxation associated with the reconstruction is not a sufficient source of energy to force the surface into the reconstructed state. (C) 1997 Elsevier Science B.V.