A novel Ni foam-Ni3 S2 @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 Ni3 S2 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 Ni3 S2 , whereas the Ni3 S2 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 Ni3 S2 @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.
Keywords: conducting materials; conductivity; electrochemical properties; graphene; sandwich architecture; supercapacitor.
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