Controlled synthesis and formation mechanism of flower-like CuS/NiS microspheres for supercapacitors

Flower-like CuS/NiS microspheres grown on nanoporous copper were successfully prepared through dealloying Ti-Cu-Ni amorphous ribbons in H₂SO₄ solution. Each microsphere is composed of many nanosheets with thickness of 17–52 nm and its main composition is CuS. We also found the formation of nanosheets highly depended on the concentration of H₂SO₄ solution during dealloying and as its concentration reached to 15 M, flower-like microsphere clusters consisting of nanosheets can be obtained. Concentration-dependent and time-dependent formation mechanism of flower-like microsphere were discussed in this work. Its formation can be divided into three steps: nucleation and growth of nanoporous copper, precipitation of transition sulfide Cu₂S and, nucleation and growth of flower-like CuS/NiS microsphere. Flower-like microsphere clusters were used as supercapacitor electrode material, which exhibit good electrochemical performance. Its specific capacitance can reach 122 F/g at current density of 1A/g and 95% capacitance retention can be maintained after 5000 cycles at 10 A/g. The high performance is due to its large specific surface area provided by the coexisting micro and nano pores.