Gamma-induced interconnected networks in microporous activated carbons from palm petiole under NaNO 3 oxidizing environment towards high-performance electric double layer capacitors (EDLCs).

Activated carbons (ACs) were developed from palm petiole via a new eco-friendly method composed of highly diluted H ₂ SO ₄ hydrothermal carbonization and low-concentration KOH-activating pyrolysis followed by gamma-induced surface modification under NaNO ₃ oxidizing environment. The prepared graphitic carbons were subsequently used as an active material for supercapacitor electrodes. The physiochemical properties of the ACs were characterized using field emission scanning electron microscope-energy dispersive X-ray spectroscopy, N ₂ adsorption/desorption isotherms with Brunauer-Emmett-Teller surface area analysis, Fourier transform infrared spectroscopy, X-ray diffraction and Raman spectroscopy. The electrochemical performance of the fabricated electrodes was investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Even treated with extremely low H ₂ SO ₄ concentration and small KOH:hydrochar ratio, the maximum S _BET of 1365 m ²  g ^-1 for an AC was obtained after gamma irradiation. This was attributed to radiation-induced interconnected network formation generating micropores within the material structure. The supercapacitor electrodes exhibited electric double-layer capacitance giving the highest specific capacitance of 309 F g ^-1 as well as excellent cycle stability within 10,000 cycles. The promising results strongly ensure high possibility of the eco-friendly method application in supercapacitor material production.
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