Lignite-derived mesoporous N- and O-enriched carbon sheet: a low-cost promising electrode for high-performance electrochemical capacitors

In the work, we successfully fabricate mesoporous N-and O-enriched carbon (NOC) with adjustable porosity and specific surface area (SSA) by using low-cost lignite as a precursor coupled with general KOH or ZnCl2 activation for electrochemical capacitors (ECs). Physicochemical and electrochemical characterizations reveal that chemical activating agents influence significantly upon the specific morphology, pore structure, and electrochemical performance of the resultant products. Strikingly, KOH-activated NOC (NOC-K) sheets are endowed with high SSA of similar to 1257 m(2) g(-1), large pore volume of 1.3 cm(3) g(-1), and optimized pore size of similar to 3 nm, rendering its electrochemical capacitance superior to those of NOC and ZnCl2-activated NOC (NOC-Z) in 6 M KOH. Thanks to its rich mesoporosity coupled with large electroactive SSA and heteroatom doping (N of similar to 4.8 at.% and O of similar to 23.3 at.%) effect, the NOC-K electrode yields even better electrochemical behaviors in 1 M H2SO4 than those in 6 M KOH.