Graphitic hierarchical porous carbons derived from lignin-hydrogels for high-performance zinc-ion hybrid supercapacitors

Porous carbon materials with tailored pore structures and optimal graphitization levels were synthesized via the calcination of a lignocellulose-based hydrogel precursor composed of alginate (AL), carboxymethyl cellulose (CMC), and potassium hydroxide (KOH) under a nitrogen atmosphere. This innovative approach significantly reduces the reliance on the activation agent KOH, achieving an efficient lignocellulose to KOH ratio of 1:0.5, and simplifies the fabrication process by eliminating the need for adhesives, merely requiring the blending of cellulose derivatives and lignin in an alkaline aqueous phase. The resulting lignocellulose hydrogel-derived porous carbons (LHPCs) demonstrate remarkable performance and durability in zinc-ion hybrid supercapacitors. Notably, LHPC900 stands out with a high specific surface area of 1722 m2 g- 1, a substantial micropore volume of 0.307 cm3 g- 1, and enhanced graphitization, rendering it an excellent candidate for the cathodes in zinc-ion hybrid capacitors with high specific capacity and superior rate performance. Moreover, LHPCs exhibit superior rate performance and exceptional long-term stability in acetonitrile electrolytes compared to aqueous counterparts, retaining 91.90 % of their capacitance after 60,000 cycles. This work presents a novel, adhesivefree, and KOH-efficient strategy for the preparation of lignin-based porous carbon materials for zinc-ion hybrid supercapacitors, suitable for both aqueous and acetonitrile-based electrolytes.