Self-Heteroatom-Doped Garlic-Derived Porous Activated Carbon for a High-Energy-Density Supercapacitor

Carbonaceous materials derived from biomass have recently gained tremendous importance. In this regard, we fabricated a high-energy-density symmetric device using garlic (Allium sativa)-derived self-heteroatom-doped activated carbon (GAC) synthesized via KOH activation at three different temperatures for supercapacitor application. The sample designated as GAC-900 with high specific surface area of 2300 m²/g and high pore volume of 1.126 cm³/g revealed the best results among the three prepared samples, with specific capacitance of 341 F/g at 1 A/g in a three-electrode configuration. It was evident that the GAC-900 material had a sufficient amount of heteroatoms of oxygen, nitrogen, sulfur and a minute quantity of phosphorous which could increase the charge storage performance by imparting pseudocapacitance. The constructed symmetric Swagelok cell GAC-900//GAC-900 device attained remarkable energy density of 33.83 Wh/kg at 600 W/kg, and significant power density of 24,000 W/kg was achieved with energy density of 14.66 Wh/kg. GAC-900//GAC-900 was tested for cyclic stability with 5000 charge–discharge cycles at 5 A/g and exhibited coulombic efficiency of 99.95% with capacitance retention of 95%. Graphical Abstract: [Figure not available: see fulltext.].