Enhancing capacity stability in redox-mediated supercapacitors through biomass selection

Abstract

Utilization of biomass resources as carbon precursor is proved as an effective strategy to synthesize activated carbon with synergy of high specific surface area, hierarchical porous architecture, self doped heteroatom content and high stability. However, lower energy density of biomass derived carbon (BDC) is still remain challenge. Herein, we synthesize biomass derived activated carbon from Xanthosoma violaceum (Blue Taro) leaf stalk (LSXV-AC) by implementing facile green synthesis approach. Owing to naturally rich porous texture, LSXV-AC posses high specific surface area of 860 m²g⁻¹ with average pore size of 2.58 nm. Also, elemental compositions and functional groups of carbon and oxygen present in sample were analysed by EDX analysis and FTIR spectroscopy. The electrochemical activities of electrode were characterized in aqueous 1 M H₂SO₄ electrolyte displays specific capacitance of 152.5 Fg⁻¹ which enhanced 7 times with addition of 0.02 M KI redox active moiety in 1 M H₂SO₄ under similar conditions at current density of 1 Ag⁻¹. The LSXV-AC electrode delivers very high specific capacitance of 985.60 Fg⁻¹ at current density of 1 Ag⁻¹ in 0.02 M KI + 1 M H₂SO₄ electrolyte with durable cycle life. Introduction of redox active moiety in aqueous electrolyte can successfully tune the electrochemical performance of activated carbon with the perspective of high specific capacitance, energy density and long cycle life. Moreover, the fabricated symmetric cell achieves highest specific capacitance of 626.08 Fg⁻¹ at 1 Ag⁻¹ with a high energy density of 36.73 Wh kg⁻¹ and power density of 1532.91 Wkg⁻¹. The symmetric cell possess exceptional cyclic stability of 97 % upto 25,000 cycles in redox mediated electrolyte. Further, the extended cell proficiently glow blue, red, green and orange LEDs manifest broad potential applicability of LSXV-AC electrode. Hence, findings of this work provides promising approach towards development of high performance supercapacitor.