Electrical and electrochemical properties of graphene modulated through surface functionalization

Abstract

The present work emphasizes a variety of electrical and electrochemical properties of graphite nano-materials (GNMs) with respect to their extent of functionalization. GNMs are prepared by chemical exfoliation of bulk graphite, where the surface chemical structure is tuned using different reaction conditions. EDS and X-ray diffraction showed variation in oxygen to carbon ratio (O : C), which suggests that GNM samples differed in the proportion of oxygenated functionalities. Raman characterization showed a decrease in I_G/I_D ratio for reduced GNMs due to reduction in sp² domain size with enhancement in overall numbers of sp² carbons. The results are also in line with I–V characteristics that manifest the linear increase in the resistivity of GNMs with increase in O : C ratio. The electrochemical response of GNMs, investigated through cyclic voltammetry, suggests that the presence of surface oxygenated functionalities of GO and SGO maintains the reversible nature of the hydroquinone redox process and also electro-catalyzes the overall process. As RGO, RSGO and CGO do not exhibit redox behavior and only show capacitive behavior, the electrochemical impedance spectroscopic results showed that these materials are highly conductive in nature, therefore do not show redox behavior.