Supercapacitors are high-power energy storage devices with far-reaching industrial applications, such as electronics, automobiles and aviation. However one of the main reasons why they have not been adopted more widely is the high cost and the difficulty of producing high-quality carbon electrodes needed to build them. But a team of scientists at Oregon State University has made a discovery that could change all that. They found a process by which cellulose heated in a furnace in the presence of ammonia can be turned into fundamental building blocks for supercapacitors. Cellulose is Earthâ€™s most abundant organic polymer and one of the key components of trees. In other words, trees could one day be instrumental in creating high-tech energy storage devices.
The approach discovered by the scientists is capable of producing nitrogen-doped, nanoporous carbon membranes, which form the electrodes of a supercapacitor, in a cost-effective and rapid way. Furthermore, the only byproduct of this process is methane, which can be used immediately as fuel, making the method very environmentally friendly.
The carbon membranes produced with this method are extraordinarily thin at the nano-scale, meaning that one gram of them can have a surface area of nearly 2,000 square meters. This is what makes them so useful in supercapacitors. The process used to create them is basically a one step reaction, which is very fast and cheap to perform.
The scientists themselves were quite surprised at their discovery. As Xiulei (David) Ji, an assistant professor of chemistry in the OSU College of Science and a team member, put it: â€œFor the first time weâ€™ve proven that you can react cellulose with ammonia and create these N-doped nanoporous carbon membranes. Itâ€™s surprising that such a basic reaction was not reported before. Not only are there industrial applications, but this opens a whole new scientific area, studying reducing gas agents for carbon activation.â€
Supercapacitors are needed primarily for devices where rapid power storage and short, but powerful energy release is required. These include computers and consumer electronics, but can also be used to power cranes, forklifts, and even defibrillators. They can also be used to open emergency slides on an aircraft and for improving the efficiency of hybrid electric cars. Supercapacitors are also capable of capturing energy that might otherwise be wasted, while their energy storage capabilities may also be used to assist the power flow from alternative energy systems, like, for example, wind energy.
Finding a cheap and environmentally benign way of producing these devices is, needless to say, a great breakthrough in the field.