We don’t talk much about graphene these days. After a furious round of excitement and research half a decade ago, the topic has largely cooled off. Part of the reason why is because it proved incredibly difficult to manufacture in quantities that were useful. Research into the material has been slow and fitful, and a group of scientists that examined the stuff actually being sold as graphene thinks it knows why: Much of it isn’t.
According to a new paper published in the journal Advanced Materials, researchers who analyzed graphene available from 60 different producers found that none of it contained more than 50 percent graphene. This is a serious issue for anyone attempting to research the properties of the material. Graphene has the incredibly electrical connectivity it does because it’s a single layer of carbon atoms. When you start stacking multiple layers on top of each other, what you have isn’t graphene anymore. It’s graphite.
The authors focused on graphene produced via Liquid Phase Exfoliation (LPE) rather than graphene produced by the original adhesive tape method, as using Scotch tape to pull graphene sheets off graphite blocks isn’t a technique that can be scaled up to mass production. But the findings indicate that the complete lack of a formal standard for what characteristics graphene should possess, as well as a lack of sub-standard classification for specific applications has led to a situation in which most of what’s being sold isn’t graphene at all. And that might explain why companies have had so little luck working with it, because what they’re actually buying isn’t the material they think it is.
Graphene’s performance is sensitive to contamination, and most of the samples the researchers tested were contaminated as well. Graphite and graphene have very different performance properties, and scattering a moderate amount of the former into the latter — something that you can’t see with your naked eye — is a great way to ruin the performance of the graphene. The authors’ write:
Furthermore, it is worrisome that producers are labeling black powders as graphene and selling for top dollar, while in reality they contain mostly cheap graphite. This kind of activity gives a bad reputation to the whole industry and has a negative impact on serious developers of graphene applications. Only through standardization and following protocols for characterization as proposed here, the graphene industry can evolve reliably.
They note that in the case of graphene contaminated with metals, the metallic particles would interfere with the performance of graphene electrodes in any battery. The final conclusion of the authors is that: “there is almost no high-quality graphene, as defined by ISO, in the market yet. The lack of properly characterized, high-quality material has been stalling the development of applications that depend fundamentally on graphene such as advanced coatings and composites, high-performance batteries and supercapacitors, etc.”
It’s not clear if this will actually lead to more use of graphene — graphene remains exceptionally difficult to manufacture and that alone could prevent it from moving out of the research lab. But given that researchers obviously won’t know if it has benefits if the material they think they’re evaluating isn’t actually graphene, finding a way to hold companies to a rigorous standard is the only way to clear the runway for actual evaluations. The authors call for the creation of production standards that can be used to quantify and accurately describe the different types of graphene that companies create, as well as for better quality control to ensure the final product is what it says it is.