Review on electrochemical impedance spectroscopy: a technique applied to hollow structured materials for supercapacitor and sensing applications

Electrochemical reactions' rate and their behavior at the electrode-electrolyte interface are better understood using electrochemical impedance spectroscopy (EIS). EIS is an analytical, electrochemical, and noninvasive technique, which provides both quantitative and qualitative analysis with higher resolution data over the traditional electrochemical techniques. It computes impedance of the concerned electrochemical system over a wide range of frequencies and measures the response (Current or voltage) with a phase shift. In this regard, this primer provides a guide for understanding the fundamentals of the EIS technique, and their theoretical background, followed by the discussion of electric circuit modeling, and deconvolution of impedance data using Nyquist and Bode plot. EIS data majorly describe the surface kinetics of the reaction, mass transport, and interpret the electronic properties of the electrode material. Thus, this review includes a detailed explanation of EIS in understanding the electrochemical behavior of electrode materials within supercapacitors and electrochemical sensing applications. The review covers the latest literature that has been done on hollow structure material and highlights their electrochemical behavior based on EIS data analysis.