Scalable Production of Hydrophilic Graphene Nanosheets via in Situ Ball-Milling-Assisted Supercritical CO2 Exfoliation

The scalable production of large quantities of defect-free graphene nanosheets (GNs) with low cost and excellent properties is essential for practical applications. Despite the highly intense research of this area, the mass production of graphene nanosheets with high solubility remains a key challenge. In the present work, we propose a scalable exfoliation process for hydrophilic GNs by ball-milling-assisted supercritical CO2 exfoliation in the presence of poly(vinylpyrrolidone) via the synergetic effect of chemical peeling and mechanical shear forces. The exfoliation difficulty has been reduced due to the intercalation effects of supercritical CO2 molecules. With the ball-milling assistance, the modifier has been introduced onto the edge or/and surface of the GNs. The process results in hydrophilic GNs with little damage to the in-plane structure. The GNs can be dispersed in various solvents with a concentration of up to 0.854 mg/mL (water) and remain stable for several months.