Electrochemical Impedance Spectroscopy as an Unorthodox Tool for Discerning Graphite, Graphene and Graphene Oxide

Exhibiting a large specific surface area, good chemical stability, high mechanical strength, flexibility, and high electrical conductivity are some of the most attractive properties for which two-dimensional (2D) materials are being investigated for a long time. Among these 2D materials, graphite, graphene, and graphene oxide (GO) are ideal for application in electrochemical energy storage, electronic, optoelectronic, spintronic devices, and sensors. But distinguishing them has always been a challenging task where spectroscopic techniques such as x-ray photoelectron spectroscopy (XPS), x-ray diffraction spectroscopy (XRD), and Raman spectroscopy have to be used. Moreover, these instruments require substantial setup conditions such as ultrahigh vacuum, for which the cost becomes a matter of concern. In this study, the 2D materials mentioned above are differentiated by an inexpensive and swift method named electrochemical impedance spectroscopy (EIS). Impedance modulus and shift-phase angle-versus frequency Bode diagram obtained from EIS are the deciding factors for discerning graphite, graphene, and graphene oxide. The time constant associated with the diffusion process through finite diffusion layers and the time constant for the charging process is responsible for the variation in plots obtained from EIS. Thus, this spectroscopic technique can be a valuable tool for researchers in determining other 2D materials in the future.