Sustainable electrode materials from biomass and silica waste: a comprehensive electrochemical study for supercapacitor applications

In this study, the design and electrochemical evaluation of sustainable carbon-silica composite electrodes synthesized from rice husk and silica sand were reported. The composites were fabricated through pyrolytic carbonization followed by controlled silica integration at various weight ratios. Structural analyses using XRD, FTIR, SEM – EDS, and BET confirmed the formation of porous frameworks and homogeneous silica distribution, particularly in low-silica samples. Electrochemical studies were carried out through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Among all formulations, the carbon – silica composite with a 95:5 ratio demonstrated optimal performance, delivering a specific capacitance of 87.61 F g−1 at 0.5 A g−1 and retaining 94.1% capacity after 1,000 cycles. CV profiles revealed quasi-rectangular shapes indicative of ideal capacitive behavior, while GCD curves showed nearly symmetrical triangular profiles, reflecting high charge – discharge efficiency. EIS measurements indicated minimal internal resistance and enhanced ion diffusion across the electrode – electrolyte interface. The synergy between well-dispersed silica dispersion and pore architecture contributed significantly to electrochemical stability and charge transport. These findings demonstrate a scalable and sustainable approach for valorizing agricultural and mineral waste into efficient energy storage materials, offering a cost-effective and eco-conscious solution for next-generation supercapacitor applications.