Design of ZIF-based CNTs wrapped porous carbon with hierarchical pores as electrode materials for supercapacitors

ZIF-8 wrapped two-dimensional ZIF-L(Co) was prepared. By adjusting the Zn 2+ concentration in precursor, ZIF-8 layer with different thickness was coated onto sheet-like ZIF-L. After carbonization, hierarchical porous carbon with CNTs wrapping was formed. Proper ZIF-8 coating would result in the porous carbon with relative high BET surface area, N content, electrical conductivity and proper pore size distribution ; thus showing higher supercapacitive performance than that of carbonized ZIF-8 or carbonized ZIF-L. The highest specific capacitance is 274 F/g for carbonized composite materials compared to that of 220 F/g for carbonized ZIF-8 and 57 F/g for carbonized ZIF-L. Moreover, such composite sample (CZ-6) showed high stability and the energy density reached 6.99 W h/kg at a power density of 0.262 kW/k, which is better than most of other ZIF-based porous carbon reported before.