A general approach to the interpretation of electrochemical quartz crystal microbalance data. Part II. Chronoamperometry: temporal resolution of mobile species transport in polyvinylferrocene films

A diagnostic procedure is developed for interpreting the response of the electrochemical quartz crystal microbalance (EQCM) to the application of a potential step. The criteria necessitate consideration of mass and a derived function, Φ, as functions of charge. The procedure for applying these criteria is illustrated by application to EQCM data for polyvinylferrocene (PVF) redox switching in aqueous NaClO₄ solutions. At high and low electrolyte concentrations, electroneutrality is satisfied mainly by counter ion motion at short times. The slowest species transferred is water. At high electrolyte concentrations, when activity constraints require salt motion, salt is transferred at a rate intermediate between that of counter ion and water. Water ingress into reduced PVF is slower than its expulsion from oxidised PVF.