DC and AC conductivities of biochar-polymer composites

We investigated the electrical conduction properties of biochar-polymer composites to understand charge transfer mechanisms. Biochar, a porous carbon from pyrolyzed organic waste, and polyvinylidene fluoride-co-hexafluoropropylene (PVD-HFP) were combined at biochar-to-polymer (B:P) ratios of 0.16:1, 0.375:1, 1:1, and 2:1. DC and AC conductivity measurements across 290 K to 430 K showed that DC conductivity (σ_dc) generally increased with biochar content, with the 2:1 ratio yielding an order of magnitude higher conductivity (~10^-3 S/cm at room temperature). Temperature dependence analysis suggests arrhenius type behavior with activation energies near ~10^-2 eV. AC conductivity followed a power law, σ(ω) ~ ω^s, with super-linear behavior (s > 1). These results will be discussed in the light of theoretical models available.