Infested ash trees as a carbon source for supercapacitor electrodes

Infested ash tree residues were carbonized at 600, 700 and 900 A degrees C. The carbonization product-biochar (BC) was investigated as a potential active material for supercapacitor electrodes in its original (o-BC) and activated (a-BC) forms. The electrodes were formed with o-BC or a-BC and a water based composite binder. The correlation between the physical properties of BC and electrochemical properties of these electrodes were carefully investigated in H2SO4 and aqueous LiN(SO2CF3)(2) electrolytes. The results obtained from cyclic voltammetry, electrochemical impedance spectrometry and charge/discharge measurements showed approximately a tenfold increase in the capacitance of the electrodes with the a-BC. Further analysis of the BC samples identified functional groups on the carbon surface of the a-BC which could be responsible for such a dramatic increase in the performance of the electrodes. The highest specific capacitances of 470 F g(-1) in 0.75 M H2SO4 and 335 F g(-1) in 3 M LiN(SO2CF3)(2) were achieved. The cycle life of electrodes with a-BC in LiN(SO2CF3)(2) electrolyte is stable and shows a very insignificant decrease in capacitive performance after 1500 cycles. These results indicate that the BC derived from infested ash trees is a promising material for use in supercapacitor electrodes.