High surface activated carbon obtained from Uruguayan rice husk wastes for supercapacitor electrode applications: Correlation between physicochemical and electrochemical properties

In this work, two different activated carbons were prepared from Uruguayan rice husk, using different carbonization times (1 and 4 h) and KOH as activating agent. The electrochemical characteristics as supercapacitor electrodes were evaluated in aqueous acidic media and correlated with their physicochemical properties, with special emphasis on the influence of the pore size. The activated carbon obtained with 4 h of carbonization time (CAct_4 h sample) presents the higher specific electrical capacitance value in three and two-electrode configuration, 248 F g(-1)@6.6 A g(-1) and 186 F g(-1)@0.9 A g(-1) respectively. This sample also showed the better rate capability and higher energy and power density (4.9 Wh kg(-1) at 192 W kg(-1)). Its best performance can be associated with its higher specific surface area (2412 m(2) g(-1)), more open microporosity (L-0 = 2.4 nm) and lower content of impurities. According to the equivalent electrical circuit model obtained from the electrochemical impedance spectroscopy, this textural characteristics determine a higher charge storage and less electrochemical resistance related to the microporosity of the sample.