A capacitance mediated positive differential resistance oscillator model for electrochemical systems involving a surface layer

We present a novel mechanism for potentiostatic current oscillations in systems involving the electrochemical formation and chemical dissolution of a surface layer on the electrode. The essential variables of the model are the capacitance of and the potential drop across the passive layer. Thus, they are both of electrical nature. We discuss the feedback loops destabilizing the stationary states and corroborate that the oscillations occur with an entirely positive faradaic impedance. Furthermore, it is demonstrated that the oscillations develop around a current plateau in a CV and that the model predicts superharmonic resonances in admittance spectra taken at a stable stationary state with oscillatory transients.