During World War II, copper, aluminum, steel and zinc became metals appropriated for military use. Around the same time, manufacturers began exploring plastics, such as acrylic, nylon, phenolic and polyethylene. Production increased, and the plastic industry flourished.
Stuart Licht, of George Washington Univ.’s Dept. of Chemistry, likened the carbon nanofiber industry to the plastics market at the beginning of World War II.
At the 250th National Meeting & Exposition of the American Chemical Society, Licht presented a method for converting atmospheric carbon dioxide into a stable, useful, compact and valuable carbon nanofiber, a substance with strength greater than steel.
“One of the great threats facing our planet is climate change,” he said. “Rather than attempt to survive the climate change consequences of flooding, wild fires, starvation, economic disruption, human death and species extinction, we must mitigate the greenhouse gas carbon dioxide.”
Previous methods of reducing carbon dioxide in the atmosphere include sequestration of the gas. According to the Environmental Protection Agency (EPA), sequestration involves capturing carbon dioxide and storing it in underground rock formations. “These formations are often a mile or more beneath the surface and consist of porous rock that holds the CO2. Overlying these formations are impermeable, non-porous layers of rock that trap the (gas) and prevent it from migrating upward,” according to the EPA.
However, Licht believes sequestration is unlikely to succeed. But converting the gas to carbon nanofibers hits two bird with one stone: lessening the presence of the gas in the atmosphere, while creating a valuable substance. Already, the substance is used in the Boeing 787 Dreamliner, high-end sports equipment and wind turbine blades, among other products, according to Licht.
In the process, carbon dioxide in collected from the air into an electrochemical reactor, which consists of two electrodes immersed in molten lithium carbonate at a temperature of 1,380 F. “Once there,” according to the American Chemical Society, “the CO2 dissolves when subjected to the heat and direct current through electrodes of nickel and steel. The carbon nanofibers build up on the steel electrode, where they can be removed.”
Power is supplied through a solar energy system, which 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,” according to the society.
Licht called the process low energy, and said the team was able to scale up production from 0.1 g of carbon nanofiber to 10 g with fair ease.
“We run this regularly under Washington D.C. sunlight,” he said, noting the urban sunlight is more than adequate to maintain the temperature for the process.
“We calculate that with a physical area less than 10% the size of the Sahara Desert, our process could remove enough CO2 to decrease atmospheric levels to those of the pre-industrial revolution within 10 years,” he said in a statement.
Compared to coal, valued at $40/ton, and graphite, $1,000/ton, carbon nanofiber’s value is $25,000/ton. This value provides a reason to explore carbon dioxide conversion into carbon nanofiber, according to Licht.
The electrical energy cost to produce the substance is estimated at $1,000/ton of carbon nanofiber.
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