Engineering biomass-derived porous carbon via pyrolysis for high-performance supercapacitors

Abstract

In the present study, pistachio shells, an abundant bio-waste, were used for the development of activated carbon (AC) using pyrolysis process. Biochar of shells was prepared at varying pyrolysis temperatures in the range 300–750 °C and then activated using KOH. The structural, functional, and morphological properties were analyzed using XRD, FTIR, and FE-SEM, along with detailed textural properties (BET surface area and pore size distribution). The electrochemical performance of working electrode was evaluated using 1 M KOH and the highest specific capacitance was obtained for the AC synthesized from biochar optimized at 600 °C (AC60), which was 304.1 F g⁻¹ at 20 mV s⁻¹ (CV) and 284.8 F g⁻¹ at 1 A g⁻¹ (GCD). The EDLC and diffusive contributions, as defined by the Trasatti method, were 79.1% and 20.9%, respectively. The fabricated symmetric device (AC//AC) offers 103 F g− 1 of specific capacitance at 0.5 A g− 1 with a maximum 14.36 W Kg−1energy density and 2500 Wh Kg− 1 power density with 80% capacitive retention after 10,000 charging-discharging cycles. The results demonstrate that AC derived from pistachio shells is a favourable electrode material for green and efficient high-performance supercapacitors.