Biomass nanoarchitectonics of hierarchically porous activated carbon prepared from palm waste fibers for high-performance supercapacitor

The activated carbon fibers (ACFs) were synthesized from Palm waste fibers using a 15 w/v% KOH solution and activated at two temperatures: 500 °C and 800 °C under vacuum conditions. Structural analysis using Fourier-transform infrared spectroscopy (FTIR) confirmed the formation of carbon structures with integrated K⁺ ions (ACK). Scanning Electron Microscopy (SEM) revealed that carbon fibers activated at 800 °C exhibit a hierarchically porous morphology. For these activated carbon fibers, the pore size increased to approximately 134 nm, and the total pore volume reached 0.981 cm³/g. Electrical conductivity measurements showed that ACK800 has a high conductivity of 0.64 S/cm, attributed to the enhanced transport of charge carriers across the well-developed porous surface. The cyclic voltammetry (CV) curve of ACK800 displayed a significant current response and the largest enclosed area among the tested samples, indicating higher capacitance than both CF and ACK500. The specific capacitance of ACK800 was measured at 223.4, 168.5, 138.5, 142.2, and 141.1 F/g at current densities of 2, 4, 6, 8 and 10 A/g, respectively. As the current density increased from 1.0 A/g to 10 A/g, the capacitance retention remained high at 97.2%, with minimal capacity loss. Additionally, ACK800 retained 95.68% of its initial discharge capacity. The coulombic efficiency of the ACK800 electrodes was approximately 97.2%, indicating excellent reversibility and stable electrochemical behavior during the galvanostatic charge-discharge (GCD) tests. The well-developed surface morphology of the activated carbon fibers highlights their potential as a sustainable material for environmental remediation and energy storage applications.