Interface Stress Measurements in an Electrochemical Environment

Abstract

The intensive parameter conjugate to surface area (often called the “surface stress,” “surface tension,” “interfacial tension,” “interface stress,” or “specific surface energy”) is an important parameter in the thermodynamic theory of solid electrodes because any interaction between the bulk solid and the remainder of the system takes place via the interface region. The thermodynamic properties of this region (i.e., the electronic conductor | ionic conductor interface, for instance the interface between a metal and an electrolyte solution) directly influence the electrochemical processes, an understanding of the thermodynamics of interfaces is of importance to all surface scientists and electrochemists. Unfortunately, a study of the interface stress of a “solid electrode” (i.e., an electrode that contains an electronically conducting solid phase in contact with an ionically conducting liquid phase) is complicated by many factors, and with the exception of a few special situations the absolute interfacial tension at the solid | liquid interface is inaccessible by experimental methods. Nevertheless, during the past two centuries several attempts have been made to derive thermodynamic equations for the solid | liquid interface, and several methods were suggested (and were supposed to be suitable) for the determination of changes in the interface stress of solid electrodes.