Apricot kernel shell–derived nanoporous activated carbon for electric double-layer capacitors in aqueous and organic electrolytes

This study investigates apricot shells as a sustainable precursor for synthesis of nanoporous activated carbon (AC) for high-performance electric double-layer capacitors (EDLCs). By separating carbonization (300–600 °C) and KOH activation, we demonstrate that carbonization temperature crucially governs the structural, chemical, and electrochemical behavior. Comprehensive XRD, FTIR, EDS mapping, and N2 sorption analyses revealed controlled tuning of the pore architecture, yielding a narrow mesopore distribution (3.5–4.0 nm). The optimized AC43 matrix (carbonized at 400 °C) achieved a specific surface area of 1200 m2/g, micropore volume of 0.47 cm3/g, and 20.8 wt.% of oxygen functionalities. In symmetric EDLC cells, AC43 delivered a stable capacitance of 88 F/g in organic LiBF4/GBL electrolyte (up to 2.4 V) and a remarkable 190 F/g in aqueous 30 wt.% KOH, exhibiting high capacitance retention and minimal voltage drop under current loads up to 360 mA/g. Optimizing pre-carbonization is a powerful strategy for designing structurally tailored biomass carbons for efficient energy storage.