How can supercapacitors help reduce global warming?
Although the nanotechnology innovation will not soak up enough carbon to solve global warming it will provide an environmentally friendly, low-cost way to make nanoporous graphene for use in supercapacitors that can store energy and release it rapidly.
The findings have been published in Nano Energy by scientists from the OSU College of Science, OSU College of Engineering, Argonne National Laboratory, the University of South Florida and the National Energy Technology Laboratory in Albany, Oregon, USA. The work was supported by OSU.
In the chemical reaction that was developed, the end result is nanoporous graphene, a form of carbon that is ordered in its atomic and crystalline structure and has an specific surface area of about 1,900 square meters per gram of material. Because of that, it has an electrical conductivity at least 10 times higher than the activated carbon now used to make commercial supercapacitors.
“There are other ways to fabricate nanoporous graphene, but this approach is faster, has little environmental impact and costs less,” said Xiulei (David) Ji, an OSU assistant professor of chemistry in the OSU College of Science and lead author on the study. “The product exhibits high surface area, great conductivity and, most importantly, it has a fairly high density that is comparable to the commercial activated carbons.
“And the carbon source is carbon dioxide, which is a sustainable resource, to say the least,” Ji said. “This methodology uses abundant carbon dioxide while making energy storage products of significant value.”
Because the materials involved are inexpensive and the fabrication is simple, this approach has the potential to be scaled up for production at commercial levels, Ji said.
The chemical reaction outlined in this study involved a mixture of magnesium and zinc metals, a combination discovered for the first time. These are heated to a high temperature in the presence of a flow of carbon dioxide to produce a controlled ‘metallothermic’ reaction which converted the elements into their metal oxides and nanoporous graphene, a pure form of carbon that is strong and can efficiently conduct heat and electricity. The metal oxides could later be recycled back into their metallic forms to make an industrial process more efficient.
By comparison, other methods to make nanoporous graphene often use corrosive and toxic chemicals, in systems that would be challenging to use at large commercial levels.
“Most commercial carbon supercapacitors now use activated carbon as electrodes, but their electrical conductivity is very low,” explained Ji. “We want fast energy storage and release that will deliver more power, and for that purpose the more conductive nanoporous graphene will work much better. This solves a major problem in creating more powerful supercapacitors.”
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