Syzygium cumini seed biochar for fabrication of supercapacitor: Role of inorganic content/ash

Syzygium cumini (Jamun) seeds were used for the preparation of biochar and application for fabrication of symmetric supercapacitor devices. Herein, two variable processes: acid pretreatment and CO2 activation, were carried out on Jamun seed-derived biochar. Acid pretreatment employed for the deashing of biochar observed partial structural collapse. CO2 activation of raw biochar at 900 °C for 1 h resulted in a higher specific surface area than that of acid-treated biochar. Electrochemical analysis of activated biochar was performed by fabricating a symmetric supercapacitor device. Activated biochar prepared after acid modification had a specific capacitance of 33.5 F/g, while activated raw biochar had a high specific capacitance of 42.3 F/g at 0.1 A/g current density, comparable to commercial activated carbon. The fabricated coin cell supercapacitor had power and energy density of 2096.5 W/kg and 19.8 Wh/kg, respectively. Thus, deashing is not necessary for the successful application of Jamun seed-derived biochar in supercapacitors as it can result in loss of structural integrity of the biochar by limiting the activation process.