The Quartz Crystal Microbalance as an In Situ Tool in Electrochemistry

By the very nature of the phenomena studied, electrochemistry deals extensively with interfacial processes. Both in application and in fundamental studies, knowledge of the types and amounts of various species which exist at the electrodeelectrolyte interface is essential to a molecular level understanding of the relationship between structure and function in electrochemical phenomena. Consequently, many different types of experimental techniques have been applied towards this end. Improvements in the sensitivity of such techniques have pushed the detection limits for interfacial species to monolayer and even submonolayer levels. This Chapter describes the use of the quartz crystal microbalance QCM to measure minute mass changes at electrode surfaces, in situ, during electrochemical processes. It will be seen that, in favorable cases, these mass changes reveal changes in the populations of interfacial species which are associated in some way with the electrochemical processes. This Chapter will focus on the considerations regarding application of the QCM to studies of mass changes at electrode surfaces during redox events and will present some representative examples illustrating what can be achieved with the method. Underpotential deposits, polymer modified electrodes are discussed.