An N,P,O-doped porous carbon electrode material derived from a lignin-modified chitosan xerogel for a supercapacitor

Lignin is a promising candidate for obtaining porous carbon materials for energy storage because it has the highest carbon content compared with the other two main components. While it is the main challenge to realize the high electrochemical performance by controlling the pore structure and improving the conductivity of carbon materials. In the present study, lignin was introduced into a chitosan solution after being chemical activated by degradation liquefaction to form a gel network with the introduction of β-glycerophosphate as a cross-linking agent. In this procedure, the formed gel network provided a basic porous structure for further obtaining highly porous carbon after the following carbonization and activation. In the same procedure, N, P, and O heteroatoms were doped in, which were efficiently preserved in the final derived porous carbon to produce the polar hierarchical porous carbon. The prepared porous carbon under optimized conditions achieved a high specific area of 2107.3 m2/g, with an average pore diameter of 3.63 nm. A high specific capacity of 534.9 F/g at a current density of 1 A/g was obtained. Simultaneously, the coin-type symmetric supercapacitors (with an ionic liquid electrolyte) based on the derived carbon also exhibit an outstanding energy density (58 Wh/kg at 375 W/kg and 11.5 Wh/kg at 4500 W/kg). This work explored an effective strategy for the application of the lignin resource in the field of energy storage materials.