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‘Diamonds from the sky’ approach turns CO2 into a valuable product

19 August 2015

A team of chemists has developed a technology to convert atmospheric CO2 directly into high value carbon nanofibres for industrial and consumer products.

Researchers are generating carbon nanofibers from CO2, removing a greenhouse gas from the air to make products (image: Stuart Licht)

“We have found a way to use atmospheric CO2 to produce high-yield carbon nanofibres,” says Stuart Licht, who leads a research team at George Washington University. “Such nanofibres are used to make strong carbon composites, such as those used in the Boeing Dreamliner, as well as in high-end sports equipment, wind turbine blades and a host of other products.”

Previously, the researchers had made fertilizer and cement without emitting CO2, which they reported. Now, the team says their research could shift CO2 from a global-warming problem to a feed stock for the manufacture of in-demand carbon nanofibres. Licht calls his approach 'diamonds from the sky'.

At its root, the system uses an electrolytic process to make the nanofibres. CO2 is broken down in a high-temperature electrolytic bath of molten carbonates at 750 degrees C. Atmospheric air is added to an electrolytic cell where the CO2 dissolves when subjected to the high temperature and direct current through electrodes of nickel and steel. The carbon nanofibres build up on the steel electrode, from where they can be removed.

To power the process, heat and electricity are produced via a hybrid concentrating solar-energy system. The system focuses the sun’s rays on a photovoltaic solar cell to generate electricity and on a second system to generate heat and thermal energy, which raises the temperature of the electrolytic cell.

Dr Licht estimates electrical energy costs of this process to be around $1,000 per ton of carbon nanofibre product, which means the cost of running the system is hundreds of times less than the value of product output.

“We calculate that with a physical area less than 10 percent the size of the Sahara Desert, our process could remove enough CO2 to decrease atmospheric levels to those of the pre-industrial revolution within ten years,” he says.

At this time, the system is experimental, and Licht’s biggest challenge will be to ramp up the process and gain experience to make consistently sized nanofibres. “We are scaling up quickly,” he adds, “and soon should be in range of making tens of grams of nanofibres an hour.”

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