Porous Carbons Derived from Lignite Mixed with Zn2+-Doped Lignin for Electric Double-Layer Capacitor

摘要

A series of porous carbons (PCs) were prepared from lignin chelating with Zn2+ and mixed with lignite. KOH was used as the activated agent during preparation process. The influences of preparation parameters including the content of lignin chelated with Zn2+, KOH/sample ratio and activation temperature on specific surface area (SSA), pore size distribution and electrochemical performances were investigated in this study. All the PCs were mainly micropores through nitrogen adsorption isotherms test. The PCs derived from the lignin chelating with Zn2+ present high SSA and total pore volume than that in the absence of Zn2+. In addition, the PC prepared from adding lignin to lignite has larger SSA than the PC prepared from lignite. The PC prepared with Zn2+ account for 30% of lignin mass, KOH/sample ratio of 3:1 and activation temperature of 700 oC has the largest SSA of 3311 m2 g- 1. When it was used as electrode for electric double-layer capacitor, the specific capacitance reached the highest value of 280.43 F g-1 at a current density of 40 mA g-1. The results demonstrate that the lignin chelating with Zn2+ then add to the lignite can significantly improve PCs performance.