ZIF-8 Nanocomposites Derived N-doped Porous Carbon And Its Electrochemical Performance

As one type of metal-organic frameworks(MOFs), ZIF-8 with abundant nitrogen atoms, high specific area, excellent chemical stability and thermostability, can be used to prepared nitrogen-doped porous carbon materials. N-doped porous carbon materials which are high specific area, pore volume and nitrogen atom, are widely used in oxygen reduction reaction and supercapacitor. This paper used cationic surfactant and polymer effectively to control the growth of ZIF-8 and synthesized ZIF-8 composites. Direct carbonization of ZIF-8 composites at a high temperature produced the nitrogen-doped porous carbon materials, and studied in their oxygen reduction performance and capacitance performance.A core-shell structure composite, zeolitic imidazolate framework@ cetyltrimethylammonium bromide(ZIF-8@CTAB) was synthesized by CTAB micelle controlling the growth of ZIF-8 in aqueous systems. Direct carbonization of ZIF-8@CTAB at a high temperature produced the nitrogen-doped hierarchically porous carbon(named as PC1000@C). In comparison with the carbonization product of pure ZIF-8(named as PC1000), PC1000@C possesses the hierarchical microporous/mesoporous structure, high surface area and favorable N species which play an active role in catalyzing oxygen reduction reaction(ORR). The specific capacitance of porous carbon was calculated from the galvanostatic-discharge curve. PC1000@C exhibits a large specific capacitance of 225 F g-1 at a current density of 0.5 A g-1 and still retains 92% of initial capacitance after 1000 galvanostatic charge-discharge cycles.As novel N-doped carbon precursors, zeolitic imidazolate framework-8@polyvinyl pyrrolidone(ZIF-8@PVP) composites were designed and synthesized. Direct carbonization of ZIF-8@PVP composites at different high temperature produced the nitrogen-doped porous carbon materials CPT(T=800, 900, 1000). And the electrocatalytic abilities of the corresponding carbonized products towards oxygen reduction reaction in alkaline solution and capacitance performance as supercapacitor electrode materials were investigated. CP1000 with the highest surface area, pore volume and quaternary-N play an active role in catalyzing oxygen reduction reaction and high specific capacitor(the specific capacitors is 198 F g-1 at 1 A g-1).By adjusting the initial dosage of PVP, three kinds of ZIF-8@PVP-n with different size and N content were prepared. CP1000-n(n=1, 2, 3) was obtained by direct carbonizing three composites at 1000°C. In comparison with the carbonized product of pure ZIF-8(named as C1000), CP1000 have the higher specific surface area and total pore volume. Favorable quaternary-N species in CP1000-n sample played an active role in catalyzing oxygen reduction reaction(ORR) and the higher specific capacitor.