Design and syntheses of Ni(OH)2@Co/C nanocomposite as electrode material for supercapacitor

A porous petal-like 3D 2-nodal (3,8)-c tfz-d metal-organic framework (MOF 1) of {[Co1.5(TCPB)(1.3-bimb)0.5·(DMF)·(dioxane)1.5]}n has been solvothermally synthesized and calcined at 700 ℃ under N2 atmosphere to obtain Co/C composite (NC1). Meanwhile, 2D flake Ni(OH)2 was in-situ coated on the surface of NC1 to prepare Ni(OH)2@NC1 composite (NC2). The structural characterization results indicated that NC1 has larger surface area and porosity compared with MOF1, and flake Ni (OH) 2 scales are anchored on the surface of NC1, which are favorable for the penetration of the electrolyte. The electrochemical measurements showed that the specific capacitance (866.8 F g−1) of the NC2-based electrode is more than three times as much as that of NC1-based electrode (264.5 F g−1), and its capacitance retention rate is 97.3% after 1000 cycles, which are mainly attributed to the fact that the pores in NC2 facilitate the diffusion of electrolyte ions, the higher surface area provides more active sites and the synergistic effect of bimetals. Also, an asymmetric supercapacitor (ASC) was fabricated with active carbon as negative electrode, NC2@NF as positive electrode and KOH aqueous solutions (1 M) as electrolyte. The energy density (E) and power density (P) of ASC were 39.7 Wh kg−1 and 213.1 W kg−1 respectively, which is comparable to that of some previously reported ASCs. Profiting from its excellent electroactivity and cyclic stability, NC2-based electrode is expected to have good application prospects in batteries, supercapacitors and other energy storage technologies.