Biomass blend derived porous carbon for aqueous supercapacitors with commercial-level mass loadings and enhanced energy density in redox-active electrolyte

Herein, oxygen-enriched porous carbon (PC-x) was prepared via co-pyrolysis, and activation of a ternary mixture of biomass (viz. sugarcane bagasse, water hyacinth, and yellow oleander). The PC-x possessed large surface area (1439–2297 m2 g−1), high pore volume, rational micro/mesopore distribution, and surface oxygen functionalities (C/O = 2.5–3.1). The optimized PC-x electrodes at commercial electrode mass loading (∼10 mg cm−2) unveiled a gravimetric capacitance of 251.6F g−1, high rate capability, and cycle stability in 6 M KOH electrolyte. The high voltage (2 V) aqueous symmetric supercapacitor fabricated in 1 M Li2SO4 electrolyte exhibited an energy density of 22.75 W h kg−1 (at 200 W kg−1) with 96.8% capacitance retention over 10,000 cycles at 5 A g−1. The energy density of the supercapacitor was augmented to 37.24 W h kg−1 (at 200 W kg−1) using 0.1 M Na2MoO4 as the redox-additive in the Li2SO4. The approach of using biomass blends offers flexibility in terms of choosing multiple waste biomass as precursors for large-scale and sustainable production of carbon materials for energy storage applications.