Absence of giant dielectric permittivity in graphene oxide materials

Graphene oxide (GO) is considered as a promising component for electronics because of its unique anisotropy, easy processing and sometimes claimed giant permittivity. The latter would arise from an enhanced electronic polarizability due to the presence of functional groups at the surface and edge of GO flakes. As a matter of fact, a number of publications have reported a very large permittivity of GO materials. Nevertheless, the reported values for the intrinsic relative permittivity vary significantly from a few units to several millions. Such variability raises a critical question on the actual and intrinsic permittivity of GO, and on difficulties of measurements due to the polarization of the electrodes. We presently report impedance spectroscopy characterizations of GO solutions with different solvents. We find very large capacitance at low frequencies, in agreement with previous reports. However, we also show that these results can be interpreted without considering a giant permittivity of GO. Actually, a simple equivalent circuit model allows us to confirm that GO does not have a giant permittivity. We conclude that GO can be used as an electrolyte for supercapacitors, or as a precursor for electrically conductive graphene-based materials, but not as an efficient additive to raise the permittivity of solvents or composites for electronics and energy storage applications.