Simultaneous Sheet Cross-Linking and Deoxygenation in the Graphene Oxide Sol–Gel Transition

Abstract

The precursor material to graphene aerogels is a hydrogel formed from an aqueous solution of graphene oxide. We investigate the time evolution of the physical and chemical properties of a graphene oxide suspension as it transitions to a hydrogel. Fully formed hydrogels undergo densification during reaction, forming mechanically stable monoliths. We demonstrate that the gelation process removes oxygen functional groups, partially re-forms the sp² network, and creates bonds between graphene oxide sheets. Furthermore, these changes to the physical and chemical properties occur on exactly the same time scale, suggesting that they have a common origin. This discovery lends greater understanding to the formation of graphene oxide-based hydrogels, which could allow more flexibility and tunability in synthetic methods for graphene-like materials