MOF-derived ZnCo <sub>2</sub> O <sub>4</sub> @NiCo <sub>2</sub> S <sub>4</sub> @PPy core–shell nanosheets on Ni foam for high-performance supercapacitors
Jiahui Zhu, Yan Wang, Xubin Zhang, Wangfeng Cai
Abstract
Abstract The ZnCo 2 O 4 @NiCo 2 S 4 @PPy core–shell nanosheets material is prepared by directly growing leaf-like ZnCo 2 O 4 nanosheets derived from the metal-organic framework (MOF) on Ni foam (NiF) via chemical bath deposition and annealing methods and then combining with NiCo 2 S 4 and PPy via electrodeposition methods. The special core–shell structure formed by MOF-derived ZnCo 2 O 4 , NiCo 2 S 4 and PPy creates a bi-interface, which could significantly promote the contact between electrode and electrolyte, provide more active sites and accelerate electron/ion transfer. And the combination of these three materials also produces a strong synergistic effect, which could further improve the capacitive performance of the electrode. Therefore, the ZnCo 2 O 4 @NiCo 2 S 4 @PPy/NiF electrode exhibits the maximum areal capacitance (3.75 F cm −2 ) and specific capacitance (2507.0 F g −1 ) at 1 mA cm −2 and 0.5 A g −1 , respectively. Moreover, its capacitance retention rate is still 83.2% after 5000 cycles. In addition, a coin-type hybrid supercapacitor is assembled and displays a high energy density of 44.15 Wh kg −1 and good cycling performance.