Superior Electronic and Dielectric Properties of Corrugated Electrochemically Reduced Graphene over Graphene Oxide Papers

Abstract

This work establishes that the frequency and temperature-dependent electronic and dielectric properties of electrochemically reduced graphene (ERGO) are higher than graphene oxide (GO) papers by 2 orders of magnitude. There is stronger polarization as a result of increased concentration of reduced clusters and thinning of graphene sheets in ERGO papers, first ever electrochemically reduced paper from GO. In GO, there is a greater dependence on frequency due to a higher percentage of interlayer O–H bonds. Dielectric permittivity increases with decreasing frequency due to stronger polarization and reduced conduction losses. At very high frequencies, greater conduction losses are responsible for lower values of dielectric permittivity of ERGO papers compared to GO papers. The "U" or "W" profile (σ vs T curves) of temperature dependent conductivity was due to thermally activated transport, residence time and ionic scattering of charge carriers. The recovery of conducting and dielectric properties at higher temperatures were due to the transition from graphene–ion–cloud to a graphene–air dielectric multi-nano-capacitor system. The latter had more sp2–carbon cluster concentration and increased electrical percolation supportive of band-like or variable range electron transport. Higher activation energies along ln σT vs T−1/2 plot are associated with delocalization of charge carriers from their potential wells, thermally activated carrier transport and frequency of the electronic field.