Electrolyte effect on the performance of carbon supercapacitor electrodes derived from Moroccan argan waste

This study focuses on the preparation of electrodes for high-performance supercapacitors and the evaluation of their performance in different electrolyte solutions (H2SO4, Na2SO4, and KOH). The activated carbon was synthesized from argan (Argania spinosa) shells using a two-step process: first, carbonization at 900 degrees C for 2 h, followed by chemical activation with phosphoric acid as the activating agent. Scanning electron microscopy (SEM) analysis revealed a varied pore size distribution; the specific surface area of 475.0055 m2/g is typically determined using the BET (Brunauer-Emmett-Teller) method. Additionally, Fourier-transform infrared (FTIR) spectroscopy identified functional groups, including C-O and C-H vibrations, while energy-dispersive X-ray (EDX) spectroscopy confirmed the predominance of carbon and oxygen, along with a small amount of phosphorus in the material. This activated carbon was then used to elaborate an electrode denoted ACPA-E. Cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy measurements indicate that ACPA-E electrode behaves as an electrochemical double-layer capacitor (EDLC) with all three aqueous electrolytes tested. The results show that the ACPA-E electrode in the H2SO4 electrolyte demonstrates a notably high specific capacitance of 154.239 F/g, which is substantially higher than the capacitance values observed in the other two electrolytes: 45.548 F/g for Na2SO4 and 27.653 F/g for KOH, at a scan rate of 10 mV/s. The results indicate that our electrode behaves as an electrochemical double-layer capacitor (EDLC) with all three aqueous electrolytes tested. Notably, sulfuric acid (1 M H2SO4) was found to be the most effective, delivering the highest specific capacitance.