Session: General Poster:

Carbon aerogels are mesoporous, three-dimensional (3D) solid materials consisting of an interconnected network of nanoscale carbon particles. Rigid carbon aerogels are mainly prepared by sol-gel chemistry and controlled removal of the liquid phase from gels with supercritical drying, and a final pyrolysis step. Flexible carbon aerogels, alternatively however, are produced by the templated assembly of one-dimensional nanofibers or nanotubes into 3D networks. Due to their unique network structure, low density and high surface area, carbon aerogels are promising materials as thermal and acoustic insulators, adsorbents, filters, catalyst supports, desalination electrodes, and electrodes for hydrogen and energy storage. Current methods to produce rigid carbon aerogels involve using resorcinol or phenol as phenolic precursors and formaldehyde as the crosslinking reagent, but they are non-renewable, toxic and expensive. Lignin, as a renewable aromatic biopolymer with high carbon content and chemical functionality, is a sustainable abundant resource for carbon aerogel production. In this study, both rigid and flexible carbon aerogels from softwood kraft lignin were created. Using sol-gel chemistry, lignin-based gels under mild conditions were synthesized with various crosslinking strategies. The effects of processing conditions, lignin content and crosslinking density on gelation kinetics and chemical and physical properties of resulting rigid carbon aerogels were shown. On the other hand, lignin is readily turned into continuous nanofibers by electrospinning and transformed into ultralight flexible aerogels without using any chemical crosslinkers. The microstructure and morphology of lignin nanofibers were tailored by heat treatment, resulting in carbon aerogels with high flexibility and significant shape recovery properties across a wide range of temperatures, also significant oil/solvent absorption from water, and electrical conductivity as functions of microstructure. Carbon electrodes assembled from these lignin-based carbon aerogels were characterized with cyclic voltammetry, galvanostatic charge-discharge tests and electrochemical impedance spectroscopy. Electrochemical tests showed that lignin carbon aerogels are promising candidates for energy storage applications such as supercapacitor electrodes.

Mi-Jung Cho

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