Ni Foam‐Ni 3 S 2 @Ni(OH) 2 ‐Graphene Sandwich Structure Electrode Materials: Facile Synthesis and High Supercapacitor Performance

A novel Ni foam‐Ni 3 S 2 @Ni(OH) 2 ‐graphene sandwich‐structured electrode (NF‐NN‐G) with high areal mass loading (8.33 mg cm −2 ) has been developed by sulfidation and hydrolysis reactions. The conductivity of Ni 3 S 2 and Ni(OH) 2 were both improved. The upper layer of Ni(OH) 2 , covered with a thin graphene film, is formed in situ from the surface of the lower layer of Ni 3 S 2 , whereas the Ni 3 S 2 grown on Ni foam substrate mainly acts as a rough support bridging the Ni(OH) 2 and Ni foam. The graphene stabilized the Ni(OH) 2 and the electrochemical properties were effectively enhanced. The as‐synthesized NF‐NN‐G‐5mg electrode shows a high specific capacitance (2258 F g −1 at 1 A g −1 or 18.81 F cm −2 at 8.33 mA cm −2 ) and an outstanding rate property (1010 F g −1 at 20 Ag −1 or 8.413 F cm −2 at 166.6 mA cm −2 ). This result is around double the capacitance achieved in previous research on Ni 3 S 2 @Ni(OH) 2 /3DGN composites (3DGN=three‐dimensional graphene network). In addition, the as‐fabricated NF‐NN‐G‐5mg composite electrode has an excellent cycle life with no capacitance loss after 3000 cycles, indicating a potential application as an efficient electrode.