Oxygen‐Rich Porous Activated Carbon from Eucalyptus Wood as an Efficient Supercapacitor Electrode

Herein, lignin‐rich KOH‐activated porous carbon from eucalyptus wood (named as PACE) is presented as an efficient electrode for supercapacitors (SCs). Compared with the most commonly used higher activation temperature, i.e., 800 °C with KOH (PACE‐800), a more efficient SC is developed by activating carbon with KOH at lesser temperature, i.e., 600 °C (PACE‐600). The high specific capacitance (i.e., 230 F g −1 at 1 A g −1 measured in a 2 m NaCl electrolyte) measured by galvanostatic charge–discharge (GCD) studies is not primarily due to larger surface area, but due to the inherent electron‐rich oxygen‐based functionalities that persist at the lower activation temperature, contributing to the hydrophilic nature to PACE‐600. The mechanism of the capacitive charge storage is deduced from electrochemical impedance spectroscopy (EIS). The application of PACE‐600 as a SC electrode is confirmed from insignificant loss in the specific capacitance after 10 000 charging–discharging cycles, recorded at 10 A g −1 . Further, fabrication of higher‐voltage (1.6 V) symmetric SC PACE‐600//PACE‐600 in aqueous neutral electrolyte (2 m NaCl) is presented, which illuminates a red LED (1.8 V) for 1 min after charging for 5 s. The corresponding energy density is calculated to be 41 W h kg −1 , and at a power density of 2396 W kg −1 .