Supercapacitors Made From Super Carbon

Simple chemical processing converts graphite oxide into a porous graphene-like carbon material with exceptional surface area and electrical properties, according to a team led by researchers at the University of Texas, Austin (Science, DOI: 10.1126/science.1200770). The development could lead to commercial quantities of this inexpensive form of carbon, which the team has shown can be fashioned into high-performance supercapacitors—devices typically made from high-surface-area carbon. Unlike batteries, which are designed to store a relatively large electrical charge and deliver energy slowly, supercapacitors deliver energy rapidly but in limited quantities. They are used in various types of electric vehicles and in consumer electronics. Yanwu Zhu, Rodney S. Ruoff, and coworkers used microwaves or heat to exfoliate graphite oxide and then treated the material with potassium hydroxide solution. The procedure formed a continuous 3-D porous network of mainly one-atom-thick carbon sheets with a surface area of some 3,100 m²/g. That value is far higher than the 1,000 to 2,000 m²/g typical of activated carbon and 500 m²/g higher than the theoretical value for graphene. Supercapacitors made from the material and subjected to standard test conditions have four times higher energy density and 10 times higher power density than today’s commercial activated-carbon supercapacitors, the team reports.