Rice husk char (RHC), a carbon-based material, was obtained by thermal decomposition of rice husk (RH) biological waste. Physicochemical properties of RHC were determined using XRD, FTIR, FESEM, TGA, N2 adsorption-desorption studies and contact angle mea­surement. A lab-scale supercapacitor (SC) was fabricated using as-prepared RHC and its super­capa­citive behaviour was investigated using techniques like CV, GCD and EIS studies. Each of RHC electrode showed a specific capacitance of 80.2 F g-1 at the constant charging/disharging current density of 0.05 A g-1. RHC exhibited 90 % retention of its initial capacitance even after 5000 GCD. The presence of amorphous SiO2 in RHC could contribute to the excellent wettability of RHC towards the water, enhancing its effective sur­face area by improving access of electrolyte ions into RHC. This remarkable super­capa­citi­ve performance of biological waste-derived RHC demonstrates its potential as a cost ef­fecttive and environ­mentally benign electrode material for aqueous electrolyte-based SCs.

A char of Tagetes erecta flowers (TFC) was derived through simple thermal decompo­sition of Tagetes erecta flowers (TF). Physico-chemical properties of as-prepared TFC were evaluated using XRD, FESEM, FTIR, TGA, N2 adsorption-desorption isotherm analysis and water contact angle measurements. The practicality and applicability of TFC as promising electrode material in supercapacitors (SCs) were evaluated in full-cell configuration by performing electrochemical characterizations like CV, GCD and EIS on a lab-scale TFC-based symmetric SC. TFC exhibited a remarkable specific capacitance of 118.4 F g-1 at a constant current density of 0.2 A g-1 and a specific energy of 4.1 Wh kg-1 at specific power of 0.1 kW kg-1. TFC showed excellent cyclic stability by retaining 92 % of its initial capacitance even after 6000 GCD cycles at 2 A g-1. The superior capacitive behaviour and cyclic stability of TFC could be attributed to its good wettability towards water. This excellent supercapacitive performance of TFC estab­lishes it as a potential floral waste-derived carbon-based electrode material for SCs.