Metal-organic frameworks-derived porous carbon nanotube for high performance supercapacitor electrode materials

The porous carbon derived from Metal Organic Frameworks (MOFs) has aroused great interest because of its considerable specific capacity and the ideal microscopic morphology. However, the structural collapse and agglomeration of MOFs during the synthesis process and annealing process could hamper the specific surface area of the derived carbon, which decreases the electrochemical performance. Therefore, a new strategy that mixing 4,4 '-Dimethyl-2,2 '-bipyridine and 1,3,5-Benzenetricarboxylic acid as mixed-ligands to stabilize the structure of the MOFs is adopted. The adding of 4,4 '-Dimethyl-2,2 '-bipyridine during the synthesis results in the N-Zn-BTC nanotube structure. Furthermore, after annealing and acid treatment, N-doped C nanotube incorporated with pore structure is formed, which shows the specific surface area of 1614.55 m(2) g(-1). The doped nitrogen element introduces the pseudocapacitance during the electrochemical process and improves the wettability of the electrode material simultaneously. And the specific capacitance of N-C electrode can reach 252 F g(-1) at 0.5 A g(-1) and maintain 98.5% of the original specific capacitance after 5000 cycles. Furthermore, a button-type symmetrical supercapacitor based on N-C electrode was assembled, which can reach an energy density of 30 Wh kg(-1) at a power density of 625 W kg(-1) and maintain 86.3% of the capacity after 2000 cycles.