The new technique, developed by a team led by researchers at the National University of Singapore (NUS), is claimed to address the long-standing challenge of efficiently processing graphene on a large-scale. It also paves the way for sustainable synthesis of the material.
The conventional method of graphene production utilises 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 is claimed to use 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 then be separated into monolayers when required or stored. It is further claimed that the slurry can be used to directly 3D-print conductive graphene aerogel, an ultra-lightweight sponge-like material that can be used to remove oil spill in the sea.
Prof Loh Kian Ping from the Department of Chemistry at NUS Faculty of Science 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.”
The research was conducted in collaboration with Fudan University, China. The findings have been published in Nature Communications.
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