Abu Dhabi-UAE: Graphene has shown tremendous promise for enhancing the functionalities/efficiencies of sensors, electronics, paints, and solar panels. Graphene consists of a single layer of carbon atoms arranged in a hexagonal shape – it makes up one layer of Graphite. Researchers are finding that adding holes to these graphene sheets could enable them to design better batteries, more efficient water filters, and new engineered semiconductors.
This new kind of graphene is not easy to make. A team of researchers at Technology Innovation Institute (TII) in the UAE has recently analyzed the best practices for making the new material and summarized the results to help inspire its development and use.
Today holey graphene (HG) is only available at the lab scale and is not commercially available. Dr. Nitul Rajput, Senior Researcher, at the Nano Material Research Group, at the Advanced Materials Research Center at the TII, said,“You must synthesize the material in your own lab. Thus, one of our objectives is to develop the material and commercialize it.”
Increasing energy density in batteries
Graphite is commonly used in energy storage as a component of many batteries. Researchers are exploring various ways to increase the energy density that can be stored within these materials. One promising technique is to embed silicon nanoparticles into graphite. Some researchers are also achieving impressive results by embedding these nanoparticles between graphene layers.
Rajput believes they can achieve even better results by finding ways to integrate silicon nanoparticles with holey graphene material. One of the problems with silicon is that it tends to expand and break apart during charging – which can cause the battery to crack and eventually, lowers the battery life.
He believes that by integrating the silicon nanoparticles into the holey graphene, the particles will navigate through the holes and fill up the space in between the graphene sheets, mitigating problems caused by expansion when the silicon captures more ions (lithiation).“This is an ideal environment for holding the lithium ions and enhancing the energy density,” he said.
Holey graphene could also be used as a material for filtering water. By controlling the size of the holes in multiple sheets layered together, some of the ions or molecules could be blocked while allowing water to pass through.
Another potential use case lies in improving the performance of semiconductors. But at this stage, most of the research is still theoretical, and experimental investigation of the semiconductor properties of HG largely remains an unexplored area open to investigation, and new discoveries.
Different manufacturing techniques
There are different ways of making holey graphene, each with relative merits. Some approaches are more precise, enabling applications in DNA analysis and semiconductors. For example, an electron or ion beam can create very precise holes. An ion beam approach can make holes in a graphene sheet of 1 cm square in about a day that may weigh a few nano-micrograms.
“These techniques are not scalable, and we cannot leverage them in large use cases,” Rajput said.
Another technique is to use thermal annealing methods for baking large-scale production of holey graphene. It is not as precise, but it is much cheaper and more scalable. Rajput's team is currently working to optimize the parameters for this approach. With the thermal process, they can create a few grams in a couple of minutes, and he believes they could scale it up to make kilograms in an hour or so.
One limitation is that this produces holey graphene in a powder form rather than as a sheet. This approach seems suitable for batteries and water filtration but might not work as well for semiconductors or DNA sequencers.
Holey graphene could play a crucial role in better batteries down the road.“If we can integrate holey graphene with silicon nanoparticle, we could enhance energy density tenfold and reduce charging time,” Rajput said.
However, there are lots of challenges, and it is not so easy to make stable components. It could take five to 10 years before this leads to commercial applications.“Stability is a big deal in battery research because you have to cycle energy storage one or two thousand times,” Rajput cautioned.
Figure: (a) Graphene with randomly distributed pores. (b) Arbitrary pores in a stack of graphene layers and the movement of ions/particles across the holes (cross-sectional view).
About Technology Innovation Institute (TII)
Technology Innovation Institute (TII) is the dedicated 'applied research' pillar of Advanced Technology Research Council (ATRC). TII is a pioneering global research and development centre that focuses on applied research and new-age technology capabilities. The Institute has seven initial dedicated research centres in quantum, autonomous robotics, cryptography, advanced materials, digital security, directed energy and secure systems. By working with exceptional talent, universities, research institutions and industry partners from all over the world, the Institute connects an intellectual community and contributes to building an R&D ecosystem reinforcing Abu Dhabi and the UAE's status as a global hub for innovation.
About Advanced Materials Research Centre (AMRC):
Advanced Materials Research Centre (AMRC) – at Technology Innovation Institute (TII) – is dedicated to breakthrough developments in smart materials with practical use-cases. With a well-funded team of internationally recognised scientists, the Centre is exploring innovations in the use of metals and composites including, meta, nano, smart, self-healing, energy absorbing, additive manufacturing, and thermoplastic materials.
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