Pyrolysis transformation of ZIF-8 wrapped with polytriazine to nitrogen enriched core-shell polyhedrons carbon for supercapacitor

This work presents a simple effective strategy to synthesize N-doped and shell-controlled carbon nanocages through a package baking approach. A green approach to synthesize core-shell ZIF-8@PTZ nanoparticles involves zinc contained ZIF-8 core wrapped by a N-enriched polytriazine (PTZ). Synthesized core-shell ZIF-8@PTZ nanoparticles are calcinated to further sublime zinc through PTZ shell and washed by HCl, leaving a porous carbon structure. At the meantime, hollow cavities were introduced into N-doped carbon polyhedrons via the sacrifice of ZIF-8 template (noted as ZIF-8@C/N-x). The electrochemical performance of the ZIF-8@C/N-x as supercapacitor electrode has demonstrated high energy density and specific capacitance, as well as a long-term cycleability showing 92% capacitance retention after 10,000 cycles. There is a systematic correlation between micro-/meso-porosity of ZIF-8@C/N-x and their electrochemical performances.