Towards Tuneable Lignin-Derived Activated Carbons for Energy Storage Applications

Nanoporous carbons offer potential solutions in many areas of energy storage, from supercapacitors to Li-battery materials, and materials for adsorptive storage of gases, such as methane and hydrogen. The performance of these carbon materials is strongly correlated to the size and geometry of their pores. Our research focuses on tuning the porosity of these carbons for different applications, just by adjusting the feedstock. Lignin, an integral part of lignocellulosic biomass, is produced in large quantities by the paper and pulping industry. The wide-spread availability and low cost of lignin makes this a promising feedstock for industrial-scale production of activated carbons. Uniquely, the lignin structure varies depending on the plant species it is isolated from. The structure of four lignins systematically isolated using the same method, but from different feedstocks, was investigated. Despite a similar chemical composition, it became clear that each lignin was composed of different numbers of aromatic units. On lignin carbonisation, only the aromatic backbone remains, thus lignin from different feedstocks is likely to produce carbons with distinct structures. Initial experiments support this possibility, since the lignins exhibited different behaviours on carbonisation. This work shows promise for using selection of the biomass feedstock to tune activated carbons porosity for different applications.