Graphene like porous carbon with wood-ear architecture prepared from specially pretreated lignin precursor

Abstract

3D graphene (or graphene-like porous carbon) is prepared from precursor lignin separated and purified from alkaline pulp black liquor. The lignin is pretreated using rapid freeze-dry technique for the porous, soft and dispersive microstructure. A special temperature control program is designed to keep the porous structure of lignin particles in the carbonization and graphitization process, avoiding agglomeration. The 3D graphene from lignin consist of curve graphene sheets in dimensions around dozen micrometers, which merge each other with clear dihedral angle and form wood-ear like architecture, different from fullerene like carbon crystals. The porous carbon is characterized and analyzed with FTIR, Raman, XRD, SEM, TEM, XPS, and SSA. A possible chemical mechanism in the synthesis of 3D graphene from lignin precursor is proposed. The aromatic groups and alkane fragments in lignin are decomposed during pyrolysis under high temperature, then the benzene rings compose the graphene sheets, and the sp3 free carbon atoms join the graphene sheets with chemical bonds along the framework of lignin polymer, forming the self-supporting and self-constructing 3D graphene, or porous carbon.