Transient electrochemical technologies have been widely applied in electrochemistry for providing time dependent information of the electrode kinetics. This review aims to show the time-frequency response behavior of an electrochemical system under periodical sine current/voltage excitations. Manifestations, numerical simulation scheme and experimental characterization methods of the nonlinear frequency response spectroscopy as well as its application in electrochemistry are addressed as the key issues. It is suggested that comparative studies between simulation and experimental data is the main way to utilize the nonlinear spectroscopy. Regulations to select current/voltage amplitude are concluded from its experimental characterization. Furthermore, it is indicated that nonlinearity of the electrochemical system arises from the electrode kinetics, which enables the nonlinear spectroscopy to own its advantages in the mechanism study and some aspects of the electrochemical system diagnosis.

Contents
1 Introduction
2 Linearity and nonlinearity of an electrochemical system
3 Manifestations of the frequency response behaviors of an electrochemical system
4 Numerical simulation and experimental characterization of the frequency response spectroscopy
5 Application of the nonlinear spectroscopy analysis in electrochemistry
6 Conclusion