Activated carbon monolith porous electrodes of a supercapacitor prepared by carbonization (N2) and activation (CO2) methods from KOH-treated pre-carbonized biomass fibers were deposited with nickel oxide at varying dipping time (from 0 to 60 min) in 20 mL of 0.1 mol Ni(NO3)2 and 20 mL of 0.2 mol NaOH solution followed by annealing at 300°C for 2 h. N2 adsorption-desorption characterization results confirmed the porous characteristic of the bare electrodes (surface area 1656 m2g-1). Energy dispersive X-ray (EDX) analysis and field emission scanning electron microscopy (FESEM) results showed the deposited nickel oxide nanoparticles were homogeneously distributed on the surface of electrodes and X-ray diffraction results revealed the semicrystalline phase of the deposited particles. Electrochemical impedance spectroscopy characterization of the supercapacitor cells fabricated using these electrodes showed that the optimum dipping time (15 – 45 min) can improve the supercapacitor specific capacitance and equivalent series resistance by 27 – 30 % and 6 – 34 %, respectively.
