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Currently, metal-organic frameworks (MOFs) have been attracting great interest as a new kind of electrode materials for energy storage devices, because their porous skeleton would benefit access and transport of electrolyte, and the exposure of metal ions can offer more active sites to electrolyte. In this study, we have successfully fabricated nickle metal-organic frameworks/carbon nanotubes (Ni-MOF/CNTs) composites, which show excellent electrochemical performance due to the synergistic effects of the Ni-MOF specific structure and CNTs with high conductivity, achieving a high specific capacitance of 1765 F g -1 at a current density of 0.5 A g -1 . To further explore the capacitive performance of the composite electrode, an asymmetric supercapacitor device using Ni-MOF/CNTs as positive electrode and reduced graphene oxides/graphitic carbon nitride (rGO/g-C 3 N 4 ) as negative electrode was fabricated, and this device could be operated at a working voltage from 0-1.6 V based on complementary potential window in 6 M KOH aqueous electrolyte, delivering a high energy density of 36.6 Wh kg -1 at a power density of 480 W kg -1 . Moreover, this asymmetric supercapacitor revealed an excellent cycle life along with 95% specific capacitance retention after 5000 consecutive charge/discharge tests. These outstanding performances would make MOFs become one of the most promising candidates for the future high energy storage systems.the chemical composition of Ni-MOF/CNTs-5 sample, XPS characterization was performed and the corresponding results are provided in Fig. 2c and 2d. It can be found that only signals from Ni, C, and O elements are detected in the survey spectrum. The high resolution Ni 2p spectrum indicates that the Ni 2P 3/2 and Ni 2P presents two distinct diffraction peaks. The stronger peak of (002) is located at about 27.3 o and attributed to the inter-planar stacking peak of aromatic systems. The low-angle reflection peak seated at 13.0 o is derived from the lattice planes parallel to the c axis.[48] The rGO exhibits a broad peak at around 23.8 o and belongs to diffraction of the (002) plane, suggesting the poor ordering of graphene sheets along 16 rGO/C 3 N 4 -3 shows the higher current density response compared to the bare rGO at the same scan rate, indicating the higher specific capacitance of rGO/C 3 N 4 -3. This appearance lies in the fact that the heteroatoms (nitrogen in the C 3 N 4 and/or oxygen on the rGO), which present electrondonor characteristics to the carbon, can not only promote the electron transfer and improve the wettability of the interface between the electrolyte and the electrode, but also generate reversible pseudocapacitance being in good agreement with the CV shape. By contrast, the smaller current density response than that of the bare rGO is observed with increasing the doped content to 4 mg and 5 mg, which is attributed to a smaller electric double-layer contribution withThe galvanostatic charge-discharge curves of all electrodes at a current density of 1 A g -1 were also measured and...

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