Synthesis of CuCo2S4 nanosheet arrays on Ni foam as binder-free electrode for asymmetric supercapacitor

Recently more and more concerns have been paid on ternary metal sulfides for use in supercapacitors because of their better electrochemical performances compared with binary counterparts. In this work, CuCo 2 S 4 nanosheet arrays on Ni foam were prepared by a sequential ion-exchange strategy under hydrothermal conditions, where Co 3 O 4 was converted into Co 4 S 3 by an anion-exchange reaction between Co 3 O 4 and S 2− ions, subsequently the Co 4 S 3 was transformed into CuCo 2 S 4 through a cation-exchange reaction with Cu 2+ ions. The as-prepared CuCo 2 S 4 was characterized by powder X-ray diffraction, high-resolution X-ray photoelectron spectroscopy, field emission scanning electron microscopy and transmission electron microscopy . The CuCo 2 S 4 arrays were composed of interconnected thin nanosheets with thickness of about 10 nm. The CuCo 2 S 4 nanosheet arrays on Ni foam were directly employed as a binder-free electrode showing a high specific capacitance of 3132.7 F g −1 at a current density of 1 A g −1 . Besides, an asymmetric supercapacitor based on this synthesized CuCo 2 S 4 electrode as positive electrode and active carbon as negative electrode can deliver a high energy density of 46.1 Wh kg −1 at a power density of 991.6 W kg −1 , and exhibits good rate capability and cycling stability.