(399b) Soft-Templated Mesoporous Carbon From Natural and Renewable Precursor

Mesoporous carbon is a different variety of synthetic porous carbon which is different from its neighbor of activated carbon owing to its large mesopore volume that finds its typical applications in myriad technological sectors. Surfactant or soft-templating of mesoporous carbon is a better alternative over hard templating owing to lower cost, easy fabrication technique and involvement of less toxic chemicals. In this technique, the mesoporous carbon is synthesized by cross-linking a suitable polymeric resin in presence of micelles of sacrificial surfactants, which give typically zero to minimal char yield. The mesoporous carbon structure is formed by harnessing the hydrogen bond between surfactant and a phenolic precursor macromolecule followed by pyrolysis leading to the removal of the surfactant and subsequent carbonization in the same step. The key role of the surfactant is very similar to that of silica for the hard template based carbons, i.e., to dictate the mesoporous structure of the carbon. Most of the precursors employed so far are synthetic phenolic type of precursor, viz, phenol, resorcinol or phloroglucinol. In this work, we have utilized a natural precursor, lignin or lignocellulose based material as carbon source along with [PEO]_a-[PPO]_b-[PEO]_a type of amphiphilic tri-block co-polymer (Pluronic) as structure dictating agent. Owing to the presence of plentiful of hydroxyl groups and ability to make intra- or intermolecular cross-linking make lignin based material an ideal natural and sustainable precursor for soft-templated mesoporous carbons. The resultant carbon possesses specific surface area of 200 to over 400 m²/g along with dominating mesoporosity. The surface area and mesopore volume were further increased with physical and chemical activation techniques, viz, by CO₂ and KOH activations. The activation process increased the surface area up to 1100 m²/g and total pore volume up to 1 cm³/g. The resultant carbon was characterized for pore textural properties, electron microscopy and small-angle x-ray scattering (SAXS). Involvement of natural and renewable materials as sources of synthetic mesoporous carbons will benefit their sustainable manufacturing and serve as inexpensive alternative precursors.