Nonlinear transient response of electrode-electrolyte interfaces

The voltage transient response, V(t), of the electrode-electrolyte interface is known to be nonlinear. It has been shown by Onaral and Schwan in 1983 that the DC limit current of linearity, IAL, is proportional to t-beta were beta is the fractional power dependence of the linear, short pulse duration impedance. We now seek to explain the physical phenomena underlying this observation. We present an equivalent circuit model of the interface and highlight the major source of the observed nonlinear behaviour. Using the equivalent circuit model and associated formulae, an expression for the limit current of linearity is derived and compared with that found experimentally by Onaral and Schwan. According to this theoretical model, a current of as little as 22 nA can be sufficient to drive an electrode system into nonlinear behaviour at longer pulse durations.