versatile building material.
A new method for taking carbon dioxide directly from the air and
converting it to oxygen and nanoscale fibers made of carbon could lead
to an inexpensive way to make a valuable building material—and may even
serve as a weapon against climate change.
Carbon fibers are increasingly being used as a structural material on
the aerospace, automotive, and other industries, which value its
strength and light weight. The useful attributes of carbon fibers, which
also include electrical conductivity, are enhanced at the nanoscale,
says Stuart Licht,
a professor of chemistry at George Washington University. The problem
is that it’s very expensive to make carbon fibers, much less nanofibers.
Licht says his group’s newly demonstrated
technology, which both captures the carbon dioxide from the air and
employs an electrochemical process to convert it to carbon nanofibers
and oxygen, is more efficient and potentially a lot cheaper than
existing methods.
But it’s more than just a simpler, less expensive way of making a
high-value product. It’s also a “means of storing and sequestering
carbon dioxide in a useful manner, a stable manner, and in a compact
manner,” says Licht. He points out that if the process is powered by
renewable energy, the result is a net removal of carbon dioxide from the
atmosphere. In a recent demonstration, his group used a unique concentrated solar power system,
which makes use of infrared sunlight as well as visible light to
generate the large amount of heat needed to run the desired reaction.
The process requires molten lithium carbonate, with another compound,
lithium oxide, dissolved in it. The lithium oxide combines with carbon
dioxide in the air, forming more lithium carbonate. When voltage is
applied across two electrodes immersed in the molten carbonate, the
resulting reaction produces oxygen, carbon (which deposits on one of the
electrodes), and lithium oxide, which can be used to capture more
carbon dioxide and start the process again.
The researchers demonstrated the ability to make a variety of
different nanofiber shapes and diameters by adjusting specific growth
conditions, such as the amount of current applied at specific points of
time and the composition of the various ingredients used in the process.
They also showed they could make very uniform fibers. Licht says the
mechanisms underlying the formation of the fibers still need to be
better understood, and he’s confident the group can keep developing more
control over the nature of the fibers it makes.
As for the technology’s emissions-cutting potential, the researchers
are optimistic. They calculate that given an area less than 10 percent
of the size of the Sahara Desert, the method could remove enough carbon
dioxide to make global atmospheric levels return to preindustrial levels
within 10 years, even if we keep emitting the greenhouse gas at a high
rate during that period.
Of course, this would require a huge increase in demand for carbon
nanofibers. Licht believes the material’s properties, especially the
fact that it is so lightweight and also very strong, will spur greater
and greater use as the cost comes down, and he thinks his new process
can help with that. Imagine that carbon fiber composites eventually
replace steel, aluminum, and even concrete as a building material, he
says. “At that point, there could be sufficient use of this that it’s
actually acting as a significant repository of carbon.”
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