A new porous carbon derived from waste Pongamia pinnata oil residue as a renewable resource for supercapacitor performance

Abstract

A significant portion of ongoing research is focused on transforming biological waste into valuable carbon compounds suitable for use in supercapacitors. However, there is a notable challenge in creating the necessary porous structure and achieving high capacitance. This study aimed to produce a hierarchical porous carbon material through a two-step chemical activation process using the leftover oil-pressed residue from Pongamia pinnata. By combining carbonization with KOH chemical activation, we successfully created a porous carbon substance with a large specific surface area of 811 m2g-1. Through electrochemical evaluations, we identified a notably high specific capacitance of 205 Fg-1 at 1 Ag-1. In a 1M Na₂SO₄ water-based electrolyte solution, a symmetrical supercapacitor made of this material demonstrated a capacitance of 87.09 Fg-1 at 0.4 Ag-1, a high energy density of 42.8 Whkg−1, and a high power density of 9.67 kWkg−1. Moreover, at a high current density of 10 Ag-1, the porous carbon material maintained a consistently stable cyclic performance, retaining 93 % of its initial capacitance throughout 5000 charge-discharge cycles. This study underscores the promising potential of utilizing porous carbon derived from oil residue in supercapacitor applications, contributing to the effective utilization of biowaste resources.