MgO-templated hierarchical porous carbon sheets derived from coal tar pitch for supercapacitors

Two-dimensional hierarchical porous carbon sheets (FHPCs) have been prepared by using nano-MgO sheet as template and coal tar pitch as carbon precursor coupled with KOH activation. The weight ratio of pitch with potassium hydroxide (KOH) exerts a marked effect on the porosity of the carbon. The FHPCs materials show some advantages for electrochemical energy storage including a specific surface area of 1454∼1604 m2 g−1, sheet structure, hierarchical porosity with macro/meso/micropores, rich O-doping (19 wt%). Resulting from the multiple synergistic effects of these advantages, the FHPC1:2 electrode can achieve a high capacitance of 290 F g−1 and 250 F g−1 at 1 A g−1, 20 A g−1, respectively, and excellent rate capability with 86% retention rate in 6 M KOH electrolyte. The FHPC1:2 symmetric supercapacitor displays a high energy density of 20.28 Wh kg−1 at a power density of 873 W kg−1 and retains as high as 8.87 Wh kg−1 at 6389 W kg−1 in 1 M Na2SO4 electrolyte. Our work demonstrates that KOH activation coupled with flake-like MgO template can act as an excellent route to prepare hierarchical porous carbon sheets from coal tar pitch for high performance supercapacitors.