Combination of redox-active natural indigo dye and bio-derived carbon from ridge gourd fruit for high-performance asymmetric supercapacitors

A low-cost, high surface area, and hierarchically porous activated carbon (ACRG-800) was derived via KOH activation and a one-step carbonization process of dried ridge gourd (RG) fruits. ACRG-800 was microporous in nature with a specific surface area of similar to 1370 m(2) g(-1). When supercapacitor (SC) electrodes were fabricated using ACRG-800, high charge storage capacity with a specific capacitance of 352 F g(-1) (at a current density of 2 A g(-1)) and 280 F g(-1) (at a current density of 2 A g(-1)) was attained in three-electrode and symmetric two-electrode system in aqueous 1 M H2SO4 electrolyte, respectively. Further, the redox-active indigo (IND) dye was mixed with ACRG-800 to obtain ACRG-800-IND. Asymmetric SC device, fabricated using ACRG-800 positive electrode and ACRG-800-IND negative electrode in 1 M H2SO4 electrolyte, exhibited high specific energy of 13.2 Wh kg(-1) at specific power of 1 kW kg(-1) when operated at 2 A g(-1) in the voltage range of 0 to 1 V. Briefly, the high surface area framework of ACRG-800 provides an outstanding electrical double-layer capacitance, while IND adds faradaic pseudocapacitance.

Automated summary

A low-cost and hierarchically porous activated carbon material ACRG-800 was obtained through the carbonization and activation of ridge gourd fruits. ACRG-800 demonstrated high charge storage capacity and specific energy in supercapacitors, and the addition of redox-active indigo dye further enhanced its performance.