A research team led by the National University of Singapore (NUS) and conducted in collaboration with Fudan University has developed an economical and industrially viable strategy to produce graphene. The new technique may offer a way for efficient large-scale production of graphene, to pave the way for sustainable synthesis of the material.
The conventional method of producing graphene utilizes sound energy or shearing forces to exfoliate graphene layers from graphite, and then dispersing the layers in large amounts of organic solvent. As insufficient solvent causes the graphene layers to reattach themselves back into graphite, yielding one kilogram of graphene currently requires at least one tonne of organic solvent, making the method costly and environmentally unfriendly.
The NUS-led development research team, in contrast, uses up to 50 times less solvent. This is achieved by exfoliating pre-treated graphite under a highly alkaline condition to trigger flocculation, a process in which the graphene layers continuously cluster together to form graphene slurry without having to increase the volume of solvent. The method also introduces electrostatic repulsive forces between the graphene layers and prevents them from reattaching themselves.
The resulting graphene slurry can be easily separated into monolayers when required or stored away for months. The slurry can also be used directly to 3D-print conductive graphene aerogels, an ultra-lightweight sponge-like material that can be used to remove oil spill in the sea.
Professor Loh Kian Ping from the Department of Chemistry at NUS Faculty of Science who also led the research said: “We have successfully demonstrated a unique exfoliation strategy for preparing high quality graphene and its composites. Our technique, which produces a high yield of crystalline graphene in the form of a concentrated slurry with a significantly smaller volume of solvent, is an attractive solution for industries to carry out large scale synthesis of this promising material in a cost-effective and sustainable manner.”