Charging Dynamic of Graphene Oxide-Water Interface Dominated by Sulfate Groups

Abstract Graphene oxide (GO) has emerged as a versatile and technologically significant 2D material due to its chemical flexibility, allowing for sophisticated structural manipulation and efficient exfoliation from graphite oxide. Despite its extensive applications, the inconsistency in various aspects of GO processing, arising from unidentified factors that impact the precise chemical structure of GO, has significantly stalled progress in the field. Herein we show that the often-overlooked organosulfate groups play a decisive role throughout the entire GO lifecycle. Their influence extends from governing charging behaviour and self-assembly to impacting material properties, which in turn affect storage, processing, and applications. Detailed elemental analysis combined with modelling results reveal a high surface charge density, explaining the spontaneous exfoliation observed in widely used methods. Understanding the chemistry of GO enables us to tailor synthesis for enhanced material stability and ionic conductivity. Our results shed light on the electrical double layer around atomically thin membranes, paving the way for further exploration into 2D polyelectrolytes.