Oxygen self-doped physalis peruviana calyx husk-derived porous carbon for supercapacitors

Physalis peruviana is a widely spread plant, and its calyx husk are rich in cellulose and hemicellulose, making it an ideal precursor for preparing supercapacitor electrode materials. The Physalis peruviana calyx husk is an excellent source of activated carbon and has a honeycomb-like epidermis, veins, and basic tissues. Its unique skeleton additionally assists to provide the material a three-dimensional structure. A series of porous carbon materials were synthesized from the calyx husk of Physalis peruviana via KOH as an activator. The variation of micromorphology, structure, and electrochemical properties of PCC-T materials with activation temperature has been investigated. The PCC-800 material prepared at 800 °C has a surface oxygen content of 11.63%, a rich pore structure (micro-meso-macroporous), and a large specific surface area (2703.75 m² g⁻¹). In 6 M KOH, PCC-800 has a specific capacitance of 349.7 F g⁻¹ at a current density of 0.5 A g⁻¹ in a three-electrode system, and a capacitance retention of 78.9% even with a 40-fold increase in current density. The assembled symmetric supercapacitor achieved an energy density of 8.95 Wh kg⁻¹ (250 W kg⁻¹) in 6 M KOH and 17.56 Wh kg⁻¹ (187 W kg⁻¹) was obtained in 1 M Na₂SO₄ electrolyte in a two-electrode system. In addition, the capacitance is reduced by only 1.4% after 6,000 charge–discharge cycles at a current density of 8 A g⁻¹.