A revolutionary new material
While sp2 and sp3 carbon allotropes are respectively well-understood as graphite and diamonds, there remains a significant gap in carbon science. “sp-hybridised carbon allotropes are the missing piece in the carbon puzzle,” says Carlo Casari(opens in new window), a physicist in the Department of Energy at the Polytechnic University of Milan(opens in new window) (Polimi). Carbon allotropes are different structural forms of the element carbon, with sp-hybridised carbon allotropes having linear or polyatomic chain structures where carbon atoms are linked by alternating triple and single bonds. According to Casari, recent breakthroughs have fundamentally transformed science’s understanding of these elusive structures. “Scientists have not only uncovered naturally occurring sp-carbon systems, but also successfully engineered new structures, bridging a critical gap in carbon-based nanomaterials,” he explains. One of those breakthroughs is amorphous graphyne (AGY), a new sp-based carbon material developed by the EU-funded SCCAMC(opens in new window) project.
A hybrid carbon membrane called amorphous graphyne
To get to AGY, the Marie Skłodowska-Curie Actions(opens in new window) (MSCA) supported project started by stabilising sp-hybridised carbon and exploring its synthesis and functional applications. Yifan Zhang, the project’s MSCA grantee, then developed chemical and physical methods for efficiently producing carbon atomic wires called polyynes. “sp-hybridised carbon in the form of chains or wires represents the ultimate one-dimensional carbon nanostructures with outstanding predicted properties,” notes Casari, the project’s principal investigator. To synthesise the polyyne, researchers developed a modified pulsed arc-discharge process capable of recycling solvent, reducing the use of chemical resources by as much as 80 %. “Crucially, we used a room temperature liquid-liquid interfacial synthesis technique that turns these polyynes into stable, wafer-sized amorphous sp2-sp hybrid carbon membranes that we named amorphous graphyne,” remarks Zhang. The project also demonstrated that the thermally treated AGY material has electrocatalytic performance and exhibits oxygen reduction reaction (ORR) activity as a metal-free catalyst. ORR is a chemical reaction where oxygen gains electrons and is reduced, typically to water or hydrogen peroxide. It is a critical process in energy conversion systems such as fuel cells.
A metal-free catalyst for sustainable energy solutions
By demonstrating AGY’s potential as a metal-free ORR catalyst, the SCCAMC project has contributed to the development of sustainable energy solutions. It has also cleared a path towards a precious metal-free fuel cell. “Just as graphene revolutionised materials science and nanotechnology, we hope our innovative, room-temperature-synthesised material will find its way into labs and applications worldwide, ultimately revolutionising flexible electronics, advanced sensors and green catalysts,” concludes Zhang.
