Sustainable lignin-derived hierarchical mesoporous carbon synthesized by a renewable nano-calcium carbonate hard template method and its utilization in zinc ion hybrid supercapacitors

Abstract

Research on zinc-ion hybrid supercapacitors has been gaining much attention due to the combination of their high energy and power density. However, the cost of preparation and poor rate performance of porous carbon cathode materials are two major issues limiting their large-scale utilization. In this study, we used nano calcium carbonate as the hard template agent and economical lignin as the carbon source to synthesize lignin-derived porous carbon with high specific surface areas and high mesopore ratios. Through a double decomposition reaction, calcium chloride produced by acid pickling is combined with sodium carbonate to create nano-calcium carbonate, thus enabling the regeneration of nano-calcium carbonate. More importantly, carbon dioxide resulting from the pyrolysis of calcium carbonate causes an internal activation effect on carbon materials, thus causing the formation of micropores and expanding the pore size of some micropores and small mesopores. Through this strategy, the specific surface area of lignin-derived porous carbon is up to 860.5 m² g⁻¹, and the mesopore volume accounts for more than 90% of the total pore volume. The zinc-ion hybrid supercapacitor with lignin-derived porous carbon as the cathode displays an impressive capacity retention rate of 64% when the current density is increased from 0.1 to 20 A g⁻¹. This work provides a green and sustainable route for the development of low-cost, high-rate performance porous carbon materials.