Porous carbon materials derived from plant biomass offer great promise towards developing sustainable functional materials for advanced applications such as energy storage, CO2 capture, catalysis supports and environmental remediation. Carbon aerogels are a unique class of porous materials owing to their tunable three-dimensional hierarchical network structure, mesoporosity, electrical conductivity and high specific surface area and pore volume. Traditionally, carbon aerogels are prepared by sol-gel processing of non-renewable and toxic phenolic precursors such as resorcinol or phenol and formaldehyde as the crosslinking reagent, followed by controlled removal of liquid phase from organic gels with supercritical drying, and heat treatment at elevated temperatures under inert atmosphere. Lignin, as a renewable aromatic biopolymer with high carbon content and chemical functionality for crosslinking, is a sustainable abundant resource for carbon aerogel production. In this study, softwood kraft lignin-based gels were synthesized with different crosslinking strategies and converted into aerogel and carbon aerogel materials with high lignin content. The effects of processing conditions, lignin content and crosslinking density on gelation kinetics and chemical and physical properties of resulting carbon aerogels are shown. The role of surface activation on the surface area, microstructure and porosity of aerogels were evaluated by nitrogen gas adsorption. Cyclic voltammetry, charge-discharge and electrochemical impedance tests showed that supercapacitors produced from lignin-based aerogels have superior specific capacitance compared to commercial resorcinol-formaldehyde-based carbon aerogel and activated carbon. Moreover, the presence of ultramicropores significantly enhanced the CO2 adsorption capacity at 100 kPa, revealed that activated lignin carbon aerogels are promising candidates as adsorbents for CO2 capture applications.

Lignin-based multifunctional carbon aerogels for energy storage and CO2 capture applications

ACS Spring 2022

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