From salt-filled ZIF-8 to open-door nanoporous carbon with optimized pore system for electrochemical supercapacitor with enhanced energy density

Zeolitic imidazolate framework (ZIF) derived carbon generally suffers from a hydrophobic close-ended microstructure, leading to poor rate capability and low energy density in supercapacitors. In view of the defects, a facile strategy is demonstrated to synthesize open-door nanoporous carbon with self-doped heteroatoms by the pyrolysis of salt-filled ZIF-8. Specifically, inert NaCl is impregnated into the channels of ZIF-8 to inhibit framework shrinkage and promote the generation of open pore system. The resultant carbon CZ-900 features with O, N co-doped surface and specific surface area of 1420 m2·g−1. It exhibits a specific capacitance of 574.9 F·g−1 at 0.5 A·g−1 in aqueous electrolyte of 1.0 M H2SO4, which is higher than other carbons derived from ZIF-8. In the two-electrode system, it shows a high energy density up to 21.1 Wh·kg−1 at a power density of 211.3 W·kg−1. The superior performances can be attributed to its integration of open-pore structure and N/O co-doped surface, which provides a fast ion-transport pathway, improved interface wettability, broadened operation potential and efficient faradic-activity.