Cellulose is the most abundant organic polymer on Earth and a major part of trees. Now, scientists at Oregon State University have discovered cellulose can be turned into electrodes for supercapacitors by heating it in a furnace with ammonia.
Supercapacitors, also known as ultracapacitors, are a type of high-power energy storage device. They have a wide range of industrial applications, from aviation to electronics to automobiles.
Unfortunately, commercial usage has been held back by their high cost as well as the complexity of producing high-quality carbon electrodes.
Nitrogen Doped Nanoporous Carbon Membranes
This new approach is able to produce nitrogen-doped, nanoporous carbon membranes, which are the electrodes of a supercapacitor, at low cost, rapidly, and in an environmentally gentle process. The only by-product is methane, which could be re-used as a fuel or for other purposes.
At the nano-scale, the carbon membranes are amazingly thin. One gram of them may cover a surface area of nearly 2,000 square meters, which is partially what makes them useful in supercapacitors.
The new process used to do this is a single-step reaction that’s fast and inexpensive. It starts with something about as simple as a cellulose filter paper, analogous to the disposable paper filter in your coffee maker.
Being exposed to high temperatures and ammonia converts the cellulose to the nanoporous carbon material required for supercapacitors. The process should allow them to be produced, in mass, more cheaply than before.
A supercapacitor can be recharged much faster than a battery and packs a lot more power. They can be used in any kind of device where rapid power storage and short, but powerful energy release is needed.
For instance, supercapacitors may be used in computers and consumer electronic devices, like a flash in a digital camera. They have applications in heavy industry, and are able to power anything from a crane to a forklift.
A supercapacitor can capture energy that might otherwise be wasted, such as in braking operations. And their energy storage abilities may help “smooth out” the power flow from alternative energy systems, such as wind energy.
They can power a defibrillator, deploy the emergency escape slides on an aircraft and significantly improve the efficiency of hybrid electric automobiles.
Nanoporous carbon materials also have other applications in adsorbing gas pollutants, environmental filters, water treatment and other uses.
Wei Luo, Bao Wang, Christopher G. Heron, Marshall J. Allen, Jeff Morre, Claudia S. Maier, William F. Stickle, Xiulei Ji. Pyrolysis of Cellulose under Ammonia Leads to Nitrogen-Doped Nanoporous Carbon Generated through Methane Formation. Nano Letters, 2014; 140401093156004 DOI: 10.1021/nl500859p
Images Credit: Oregon State University