Green fabrication of copper/carbon aerogel composite from water hyacinth waste with PVA/CMC reinforcement: Correlation between structural optimization and electrochemical behavior for supercapacitor application

This study developed eco-friendly aerogel electrodes for supercapacitors with high capacitance, energy density, and cycling stability. Water hyacinth, a biomass waste, was converted into carbon aerogel (CA) via gelation, freeze-drying, and pyrolysis. A copper-doped carbon aerogel (Cu/CA) was synthesized through carbonization under N2 and subsequent wet impregnation using Cu(NO3)2·3H2O. The materials were characterized by SEM-EDS, TGA, and BET analyses to determine morphology, composition, and surface properties. Electrochemical behavior was examined by Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV), and Galvanostatic Charge-Discharge (GCD) in H2SO4 and KOH electrolytes. The cellulose aerogel with a PVA/CMC ratio of 80/20 exhibited the lowest density (0.0357 g/cm³) and highest porosity (97.29%). CA800 showed a type IV isotherm with both micro- and mesopores and a surface area of 252.6 m²/g. Among all samples, Cu/CA-20 (20 wt% Cu) delivered the highest specific capacitance 362.18 F g-1 (CV, 10 mV/s) and 269.33 F g-1 (GCD, 0.5 A/g). Notably, the electrode also demonstrated excellent long-term durability, retaining approximately 96.77% of its initial capacitance after 5000 continuous charge–discharge cycles. The enhanced performance resulted from the pseudocapacitive contribution of copper species, demonstrating that Cu/CA-20 is a promising electrode material for high-performance supercapacitors and sustainable energy storage applications.