Green light for carbon science

Carbon is everywhere – one of the most abundant elements, the basis of life on Earth, and central to global environmental concerns. It has even won a Nobel Prize or two. Ten years after the discovery of graphene and more than 30 years since the first report of C₆₀, what is next for carbon?

“We have seen a remarkable series of discoveries in carbon materials over the last two decades… [and it] continues to be an exciting field with great prospects,” says Robert Hurt of Brown University and Editor-in-Chief of the journal Carbon. With the journal’s expert board of editors, he has spotlighted what those prospects – and inherent challenges – could be [Zhang et al., Carbon 98 (2016) 708].

Carbon, here, means solid phases of the material, from 0D fullerenes through 1D nanotubes and 2D graphene to 3D structures. These materials are finding a plethora of applications in environmental, as well as other, technologies as key components of batteries, fuel cells, supercapacitors, and electrolytic cells for producing hydrogen from water.

The unique combination of electrical conductivity, low density, and chemical stability hold potential for transparent solar cells, catalysts for industrially relevant reactions such as carbon dioxide reduction to fuels and chemicals, and lightweight composites that reduce fuel use in cars and aircraft. Next-generation carbon materials could also prove ideal for electrochemical energy storage systems, although careful selection of the right carbon material for the right application is needed.

There is resurgence of interest in carbon fibers, along with newcomer graphene, as additives to composites. Fibers with improved properties that can be produced from cheap and sustainable sources are more and more desirable in today’s energy-conscious world.

“There is much interest now in applications – turning new carbon materials from the last decades into viable, sustainable technologies,” says Hurt, who believes that the challenge will keep the R&D community busy for years to come.

But another Editor of Carbon, Mauricio Terrones, thinks carbon still has more surprises in store.

“I am certain that there will be new carbon forms made with fascinating properties different from those we know now,” he says.

Carbon nanotubes and graphene could be used as building blocks to create uniquely complex 3D architectures, he points out, which might offer unprecedented new properties or material phenomena. Porous structures produced in this way, for example, could be uniquely useful for treating or protecting increasingly precious air and water resources.

Underpinning all this, however, must be reliable, cost-effective means of production.

“Controlling carbon-carbon bonding to make new carbon allotropes is a challenge,” admits Terrones. “We might need to develop completely new synthetic routes or find ways to cleverly modify current ones.”

High-yield, high-purity production processes for single-walled carbon nanotubes, for example, are still lacking. New catalysts are needed to produce nanotubes with predetermined chirality – which defines their semiconducting or metallic character – or an efficient means of sorting one from the other. Meanwhile, chemical approaches using the benzene ring as a basic building block could become an important route for the bottom-up synthesis of atomically precise graphene nanostructures.

“Carbon is an ancient element but it is still showing us it can be used to make different forms with unique properties/applications,” says Terrones. “The quest for new and unprecedented carbon materials will continue to keep science and technology moving forward.”