Highly-microporous carbon created by mechanochemical recycling herbal waste for supercapacitor with superior energy density

A sustainable method for synthesizing highly microporous carbon from recycled biomass waste is an efficient way to repurpose waste resources and produce a promising material for supercapacitor (SC). Herein, a mechanochemical approach was developed to create porous carbon by mixing Plantago seed waste (PS) with K₂CO₃ activator through ball milling, followed by carbonization and water washing, in which over 95 % K₂CO₃ can be recovered. The resulting products exhibit a microporosity ratio exceeding 90 %, hydrophilic surface, amorphous structure, and abundant oxygenic groups. Due to its high microporosity, the symmetric supercapacitor tests revealed that the PSC could store energy across a wide voltage range of 0–4.0 V in a 1.0 M TEABF₄/AN electrolyte, achieving a remarkable energy density of 78.1 Wh/kg at a power density of 2000 W/kg. These results highlight the superior energy storage capabilities of the PSC compared to other carbon-based SCs, including an industrially utilized activated carbon (YP-80F) based SC with energy density of 40.6 Wh/kg at 1500 W/kg. This research demonstrates great potential for practical energy storage applications using the developed material.