Swedish researchers have created a green alternative to reduce their dependence on mining graphite, the raw cause behind the next mysterious material, graphene oxide.
The team at the KTH Royal Institute of Technology has developed a reproducible, scalable method for producing graphene (GO) nanosheets from commercially available carbon fibers, marking a breakthrough in sustainable nanomaterial synthesis.
This process involves peeling off the carbon fibers with nitric acid. This provides high yields of thick graphene oxide sheets with properties comparable to commercial GOs fed from mined graphite.
Current graphene production problems
Graphene oxide is a widely studied nanomaterial that can be used in car batteries when thin sheets stack together to form graphite-like layers.
It is also useful for high-performance composite materials, water purification and electronic devices. However, synthesis from mined graphite requires harsh chemicals, and variations in the purity of the graphite often cause material contradictions.
Richard Olson, professor of polymer materials at KTH, says the proof of concept was made with carbon fibers derived from polyacrylonitrile (PAN), a widely available polymer that undergoes high temperature oxidation and graphitic flames.
He said the method can be replicated with other raw sources, such as raw sources such as biomass and aspects of the forest industry.
Used with EV batteries
Olson points out the electric vehicle battery market as a way to benefit from new technologies.
“The core of the graphite battery function is in the internal layered graphene, which can be harvested from commercial carbon fiber using this method,” he explained.
“The future of car manufacturing will be built on battery-based power, and the question is where graphite will be delivered. They will need a replacement.”
Conversion of carbon fibers for green production
This method consists of converting carbon fibers using a process of electrochemical oxidation in a water and nitric acid bath.
The bath acts as a conductor, and when current is sent through the carbon fiber, the material begins to lose electrons. This converts the surface just like rust on a car.
In this case, the conversion will cause the nanoscale graphene oxide layer to peel off from the surface of the carbon fiber.
In this study, only 5% of nitric acid was found to be the perfect window for creating these small nanosheets, ranging from 0.1 to 1 micrometer in size and a uniform thickness of approximately 0.9 nanometers.
In particular, Go Nanosheets synthesized in this way appeared in circular and elliptical shapes, in contrast to the typical polygonal shapes of GO synthesized from natural mined graphite.
Compared to existing synthetic methods, the new approach offers a high yield of 200 milligrams of GO per gram of carbon fiber. This efficient conversion rate makes it feasible in large-scale production and addresses the key challenges of nanomaterial synthesis.
Ensuring quality standards for new graphene nanosheets
To ensure that graphene oxide nanosheets met quality standards, researchers used many advanced techniques to examine and measure the properties and structure of the material.
In this study, we also investigated how to remove the protective polymer coating from commercially available carbon fibers prior to oxidation, heated at 580°C for 2 hours, and obtain impact heat at 1200°C for 3 seconds.
This study demonstrated that the electrical conductivity properties within graphene fibers play an important role in the electrochemical peeling process.
Olson concluded that the next step in this study included investigating bio-based sources of carbon fiber, and digging deeper into how the process works.
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