Wood Biochar Use in Supercapacitors

three researchers standing in the ISTC laboratoryJunhua Jiang (right) and two graduate students Lei Zhang (left) and Xinying Wang (center) who developed biochar supercapacitors. (Photo by L. Brian Stauffer - U. of I. News Bureau)

 ISTC researchers investigated the use of wood biochar in supercapacitors. Many supercapacitors today use activated carbon, which is typically derived from fossil fuel products. By using wood biochar instead of fossil fuels the supercapacitors and the products they comprise become more sustainable. Also, activated carbon is often treated with harsh chemicals to prepare it for use in supercapacitors and these chemicals can be avoided when using wood biochar.

When wood is pyrolysized, it maintains it highly ordered macropore structure and becomes 98 wt% carbon (the rest being oxygen). The wood biochar has a specific surface area of 400 m2 g-1 which is similar to activated carbon (~500 m2 g-1).

In addition the wood biochar electrodes have a potential window of 1.3 volts and exhibit typical rectangular-shape voltammetric responses and fast charging-discharging behavior (14 F g-1 gravimetric capacitance). If the wood biochar is modified with a weak nitric acid solution the capacitance increases seven-fold (115 F g-1). Both the original wood biochar and the modified wood biochar electrodes were stable for 5000 charge-discharge cycles without performance decays.

All these properties make wood biochar a good potential replacement for activated carbon.

This research was funded by the Illinois Hazardous Waste Research Fund and the HeteroFoaM Center (an Energy Frontier Research Center funded by the U.S. Department of Energy’s Office of Basic Research; award #DESC0001061).