Replacing Graphene with Hemp for Supercapacitors
Many consider graphene to be a wonder material, with its amazing electrical, optical, and mechanical characteristics. For that reason it is being investigated for many uses, including in supercapacitors. As reported by the American Chemical Society, graphene may soon have a serious competitor for supercapacitor electrodes from hemp.
Before we get too far, it is worth stating that it is not hemp, but a cousin of the plant that can be turned into a drug. The researchers decided to investigate hemp bast fibers, from the inner bark of the plant, to see if they could be processed into a form of carbon similar to graphene. Graphene already makes an ideal electrode for supercapacitors, but is expensive to make. A hemp-based alternative would be less expensive, especially bast as it is typically discarded by the industries that use hemp to manufacture products. What the researchers found is that if the fibers were heated to over 350 ºF and then heat with more intense heat, what material was left would exfoliate useable carbon nanosheets.
When the researchers tested the electrodes with an ionic liquid electrolyte, they found that they can match and even surpass graphene electrodes. It already supplied two to three times the energy density of modern supercapacitors at 12 Watt-hours per kilogram, and has an operating temperature range from freezing to 200 ºF.
Source: American Chemical Society