• Green tea waste converted into N-doped carbons for circular energy storage. • KOH and ZnCl 2 tuning pore morphology and graphitic integrity in biomass carbon. • Dual-step synthesis via oxidation and annealing optimizes nitrogen retention. • Achieved 128.08 F/g capacitance and 77.06 mWh/g energy density. • Exceptional 99% capacitance retention during long-term electrochemical cycling. Sustainable energy storage requires low-cost and eco-friendly electrode materials with excellent electrochemical performance. Biomass-derived carbons provide a renewable alternative, but their performance depends on activation chemistry and precursor structure. This study investigates the effects of activating agents (KOH and ZnCl 2 ) and precursor origin on the electrical properties of nitrogen-doped activated carbons. Carbon materials were synthesized by pyrolysis at 800 °C and then chemically activated. Physicochemical and electrochemical tests were performed to understand the structure–function relationships. The as-synthesized samples showed the highest specific capacitance of 128.08 F /g, an energy density of 77.06 mWh /g, and excellent cycling stability of 99% retention. ZnCl 2 activation promoted mesopore formation and nitrogen retention, enhancing charge storage and ion transport. The results indicate that biomass-derived precursors provide a scalable and efficient route to the production of porous materials. Heteroatom-doped carbons modify high-performance supercapacitors. This advancement supports energy sustainability and the value of agricultural waste, promoting affordable, clean energy and responsible consumption and production.
Sirirak et al. (Fri,) studied this question.