Electrical Conductivity of Wood-derived Nanoporous Monolithic Biochar

The electrical conductivity was exploited to establish monolithic biochar as a low-cost, high-performance material for electrochemical applications like supercapacitors. With a focus on the structure-property relationship, the effects of precursors and pyrolysis conditions were investigated, with four hardwoods, three softwoods, and one grass. The electrical conductivity of biochar monolith increased with temperature due to simultaneous increases in the degrees of carbonization and graphitization. X-ray diffraction and Raman spectroscopy revealed the growth of graphite nano-crystallites in an amorphous carbon matrix of biochar. Monolithic biochar conductivity is anisotropic; axial is more conductive than radial orientation. Moreover, the conductivity is uniquely dimension-dependent. A 2-D resistor network model was developed where the biochar is represented by a matrix of resistors in axial and radial directions. Model simulations and experiments reveal that anisotropic morphology, preferred orientation of graphite nano-crystallites and broken electron paths in the monolithic biochar are all responsible for its unique conductivityM.A.S