Graphene reflux: improving the yield of liquid-exfoliated nanosheets through repeated separation techniques

Abstract

Scalable production of graphene through liquid-phase exfoliation has been plagued by low yields. Although several recent studies have attempted to improve graphene exfoliation technology, the problem of separating colloidal nanosheets from unexfoliated parent material has received far less attention. Here we demonstrate a scalable method for improving nanosheet yield through a facile washing process. By probing the sedimentation of liquid-phase exfoliated slurries of graphene nanosheets and parent material, we found that a portion of exfoliated graphene is entrapped in the sediment, but can be recovered by repeatedly washing the slurry of nanosheet and parent material with additional solvent. We found this process to significantly increase the overall yield of graphene (graphene / parent material) and recover a roughly constant proportion of graphene with each wash. The cumulative amount of graphene recovered is only a function of total solvent volume. Moreover, we found this technique to be applicable to other types of nanosheets such as boron nitride nanosheets.

Microfluidic-Oriented Synthesis of Graphene Oxide Nanosheets toward High Energy Density Supercapacitors

“…In particular, the easy processing nature can enable GO to be constructed into different dimensions (1D fiber, 2D film, and 3D aerogel) through the reduction reaction. − According to the exfoliated mechanism (the generation of oxygen-containing functional groups between graphene interlayer), the chemical exfoliation can be classified into the oxidation–reduction method, electrochemical method, and liquid phase exfoliation method. − In this respect, the electrochemical method can ensure the formation of graphene aqueous solution by intercalating sodium dodecyl sulfate (SDS) into the graphite electrode . Additionally, the liquid phase exfoliation method is also demonstrated to synthesize few-layer graphene by employing a surfactant solution . However, the low overall yields of the electrochemical and liquid phase exfoliation methods are the major bottlenecks.…”

“…22 Additionally, the liquid phase exfoliation method is also demonstrated to synthesize few-layer graphene by employing a surfactant solution. 23 However, the low overall yields of the electrochemical and liquid phase exfoliation methods are the major bottlenecks. The oxidation−reduction method (also called the Brodie approach and the Hummers approach) mainly utilizes the strong oxidant (potassium chlorate (KClO 3 ) or potassium permanganate (KMnO 4 )) to oxidize graphite under strong acid conditions, 20 and then the GO is reduced to rGO with the aid of chemical reductants.…”

Gas-exfoliated porous monolayer boron nitride for enhanced aerobic oxidative desulfurization performance

“…Beside artificial construction of highly active h-BN catalysts, exfoliation of bulk ones into few-layered ones seems to be more efficient and easily to be realized. Most of exfoliation methods of h-BN nanosheets focused on either solid-phase mechanical method or liquid-phase exfoliation [32][33][34][35][36]. However, both of them have some inherent shortages, including ultra-low yield, expensive equipment, and toxic chemical reagents, etc [37][38][39][40][41][42][43].…”