TPT January 2021

G LOBA L MARKE T P L AC E

“Nanoribbons allow us to chemically access a wide range of structures using bottom-up fabrication, something not yet possible with nanotubes,” Mr Crommie said. “This has allowed us to basically stitch electrons together to create a metallic nanoribbon. This is one of the grand challenges in the area of graphene nanoribbon technology and why we are so excited about it.” Metallic graphene nanoribbons, which feature a wide, partially-filled electronic band characteristic of metals, should be comparable in conductance to 2D graphene itself. Fischer explained that carbon-based computers could potentially perform many times faster than current silicon- based computers while using only fractions of the power. Graphene is a leading contender for these next-generation, carbon-based computers. Narrow strips of graphene are primarily semiconductors, however, and the challenge has been to make them also work at opposite extremes, as insulators and metals, so as to be able to construct transistors and processors entirely from carbon. Several years ago Fischer and Crommie teamed up with theoretical materials scientist Steven Louie, a professor of physics at UC Berkeley, to discover new ways of connecting small lengths of nanoribbon to reliably create the full spectrum of conducting properties. In their new work they use a similar technique to stitch together short segments of nanoribbons to create a conducting metal wire, tens of nanometers long and barely a nanometer wide. The researchers are now working with electrical engineers at UC Berkeley to assemble a “toolbox” of semiconducting, insulating and metallic graphene nanoribbons into working transistors. Crommie, Fischer and their colleagues at UC Berkeley and Lawrence Berkeley National Laboratory reported their findings in the publication, Science. Energy storage with food for thought Researchers at Graz University of Technology (TU Graz) in Styria, Austria, have found a way to convert the aromatic substance vanillin into a redox-active electrolyte material for liquid batteries. The technology is an important step toward ecologically sustainable energy storage. “It is groundbreaking in the field of sustainable energy storage technology,” enthused Stefan Spirk from the Institute of Bioproducts and Paper Technology (BPTI) at TU Graz. Mr Spirk and his team have succeeded in making redox-flow batteries more environmentally friendly by replacing the core element, a liquid electrolyte of mostly ecologically harmful heavy metals or rare earths, with vanillin, an organic compound and primary component of extract of vanilla beans. A flavouring in common use, vanillin is among the few fine chemicals produced from lignin. Spirk’s team refine lignin into vanillin and then into a redox-active material, using mild and green chemistry without the use of toxic and expensive metal catalysts, so that it can be used in flow batteries. The process works at room temperature and can be implemented with common household chemicals. Vanillin is also present in large quantities. As Spirk commented: ”If you want you can even buy it in the supermarket, but we can also use a simple reaction to separate it from lignin, which in turn is produced in large quantities as waste product in paper production.”

The separation and refining process has been patented, and the test results were published in the journal Angewandte Chemie International Edition. For the future the researchers want to commercialise the technology, especially as the process is highly scalable and suitable for continuous production. Mr Spirk explained: “The plan is to hook up our plant to a pulp mill and isolate the vanillin from the lignin that is left over as waste. Whatever is not needed can subsequently flow back into the regular cycle and be used energetically, as usual. We are in concrete talks with Mondi AG, a leading global manufacturer of paper-based products, which is showing great interest in the technology.” For its final implementation the technology will need to be tested in a real-life operation. The start-up company is looking for energy suppliers to integrate the redox flow technology into their infrastructure and so relieve the burden on the grid. Spirk is convinced of its future success: “We can keep the value chain ranging from the procurement of raw materials and components to the generation of electricity on a regional basis, enable storage capacities of up to hundreds of MWh, relieve the strain on the electricity grid, and make an important contribution to green energy storage.” Redox flow technology is an important move forward for the expansion of renewable energies such as wind and solar power, demanding as it does the storage of large amounts of energy, to cushion voltage peaks in the power grid. The batteries are also suitable as backup storage for stationary applications such as power plants, hospitals, mobile phone systems or e-fuelling stations. Redox flow batteries are more easily scalable, less toxic, more recyclable and more fireproof than lithium-ion batteries, with advantages of long life expectancy and low self-discharge. Tr anspor t UK’s first hydrogen train hits the rail network The UK’s first hydrogen-powered train, Hydroflex, is running on mainline rail tracks in the English Midlands. Hydroflex was developed by the rolling-stock company Porterbrook and the University of Birmingham. Porterbrook will continue to work with academics to develop a hydrogen and battery powered module that can be fitted underneath the train, freeing up more space for passengers, but has already announced plans to put Hydroflex trains into production “in response to customer demand”. “The Hydroflex project is a great example of how world class [research and development], together with the right industry partnerships, can deliver decarbonisation technologies that are both innovative and practical,” said Professor Stephen Jarvis, head of the College of Engineering and Physical Sciences at the University of Birmingham. Several hydrogen train projects are underway in Britain, and plans for the mainline trial were announced in April 2020. Mick Cash, general secretary of the National Union of Rail, Maritime and Transport Workers (RMT) that represents the transport sector, called for future hydrogen trains to be

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JANUARY 2021