Porous Carbons Derived from Lignin

Abstract

Porous carbons are receiving great attention by scientists due to their tunable physicochemical and textural properties. In this work, lignin was activated with potassium bicarbonate (KHCO3) in order to generate porous carbons via a one-step carbonization route. The lignin-to-KHCO3 ratio affects the performance both in super capacitors and oxygen reduction reaction (ORR) electrocatalysis. The lignin-derived carbons obtained at lignin/KHCO3 mass ratios of 1:0.5 (LAC-0.5) and 1:2 (LAC-2) comprised of mesopores and micropores displaying BETs of 1558 m2g-1 and 1879 m2g-1, respectively. LAC-2 electrode material exhibited a superior specific capacitance in 2.5 M KNO3 electrolyte. A symmetric supercapacitor with LAC-2 electrodes was built displaying a specific capacitance of 28.5 F g-1. This value corresponds to an electrode specific capacitance of 114 F g-1 and a specific energy of 10 Wh kg−1 with a corresponding specific power of 397 W kg−1. Durability tests showed that the device was able to maintain a capacitance retention of 84.5% after 15,000 charge-discharge cycles. The lignin-derived carbons were also studied as electrocatalysts for ORR in a neutral medium. The LAC-2 showed higher electrocatalytic activity and superior ORR performance than LAC-0.5. The interconnected porous network and the high surface area made the lignin-derived porous carbons suitable electrode materials for dual applications.