Hierarchical NiCo2S4/NH2-UIO-66 nanoflower composites coupled with S, N-doped carbon for hybrid supercapacitors

NH 2 -UIO-66 has been regarded as a promising porous material owing to its high specific surface area and structural stability, although its limited conductivity restricts its application in supercapacitors. In this work, a NiCo 2 S 4 /NH 2 -UIO-66 nanoflower composite (NCS/NU) was synthesized via a vulcanization process with thioacetamide. Electrochemical measurements conducted in a three-electrode system revealed that the composite delivered a specific capacitance of 172.4 mAh g −1 at 1 A g −1 and maintained 82.1% of its initial capacitance after 5000 cycles at 5 A g −1 . Morphological characterization indicated that the nanoflower architecture was largely preserved after sulfurization. The in-situ formed NiCo 2 S 4 contributed to enhanced pseudocapacitance and induced surface wrinkling of the petals, which helped stabilize the composite structure supported by NH 2 -UIO-66. For the anode, S and N co-doped three-dimensional porous carbon (SNC) was prepared via a sol-gel method followed by stepwise high-temperature carbonization using ammonium persulfate as the activator. A hybrid supercapacitor was subsequently assembled with the NCS/NU as the positive electrode and SNC-700 as the negative electrode. The device delivered an energy density of 28.8 Wh kg −1 and retained 74.1% of its initial capacitance after 5000 charge-discharge cycles.