Code in support of: Physical and chemical mechanisms that influence the electrical conductivity of lignin-derived biochar

<p>Lignin-derived biochar is a promising, sustainable alternative to petroleum-based carbon powders (e.g., carbon black) for electrode and energy storage applications. Prior studies of these biochars demonstrate that high electrical conductivity and good capacitive behavior are achievable. These studies also show high variability in electrical conductivity between biochars (~10^-2-10^2 S/cm). The underlying mechanisms that lead to desirable electrical properties in these lignin-derived biochars are poorly understood. In this work, we examine the causes of the variation in conductivity of lignin-derived biochar to optimize the electrical conductivity of lignin-derived biochars. To this end, we produced biochar from three different lignins, a whole biomass source (wheat stem), and cellulose at two pyrolysis temperatures (900 C, 1100  C). These biochars have a similar range of conductivities (0.002 to 18.51 S/cm) to what has been reported in the literature. Results from examining the relationship between chemical and physical biochar properties and electrical conductivity indicate that decreases in oxygen content and changes in particle size are associated with increases in electrical conductivity. Lignin isolated with an acidification process yielded biochar with higher electrical conductivity than lignin isolated with sulfate processes. These findings indicate how lignin composition and processing may be further selected and optimized to target specific energy-related applications.</p>