Contribution of electron localization and delocalization zones in the performance of electrochemically reduced graphene oxide based supercapacitors: An experimental and the first-principles study

Abstract

Graphene oxide (GO) has been investigated as a promising electrode material for supercapacitors due to its intriguing physical and chemical properties. However, the interpretation of the pseudocapacitance and charge storage mechanism in GO and its derivatives is still debated and is yet to be understood. Here, we report a detailed and comprehensive analysis of the pseudocapacitive charge storage mechanism in GO and electrochemically reduced GO electrodes using cyclic voltammetry, electrochemical impedance spectroscopy combined with first principles calculations. Contrary to conventional believes, our results reveal that pseudocapacitive charge storage mechanism is due to conduction built by the electron delocalization region in GO during reduction rather than localized electron transfer. It is observed that the removal of oxygen functional groups from the surface of the GO leads to decrease in diffusion current and the reconstructed electron delocalization region contributes to increased specific capacitance. This work provides a clear and fundamental understanding of pseudocapacitive charge storage mechanisms in GO derivatives that will be also helpful in exploration of GO-based novel and hybrid electrode materials for high-performance supercapacitors.