Interfacial Phenomena Governing Performance of Graphene Electrodes in Aqueous Electrolyte.

There is evidence of the presence of intercalated water between graphene and the substrate in electronic devices. However, a proper understanding of the impact of this phenomenon, which causes important limitations for the optimization of graphene-based devices operating in aqueous electrolytes, is missing. We used graphene-based electrodes on insulating and conducting substrates to evaluate the impact of intercalated water by combining experimental techniques with numerical simulations. Results show that the capacitance of the conductive substrate/graphene electrodes is significantly higher than that of the insulating substrate/graphene ones. Meanwhile, Raman spectroscopy demonstrates that graphene charge modulation with the applied potential is independent of the substrate conductivity. We found that this intriguing behavior is influenced by the water intercalation phenomena and governed by the substrate conductive nature. This work contributes to the understanding of the electric response of graphene-based devices in an aqueous environment and of the methods to measure and model it.