Facile Synthesis of Ultrathin CuCo2S4 Nanosheets for High-Performance Supercapacitors

Two-dimensional (2D) structural CuCo2S4 exhibits great potential for applications in the renewable energy and catalysis fields. However, the fabrication of CuCo2S4 nanosheets remains a great challenge, and studies focussed on CuCo2S4 nanosheets used for supercapacitors are seldom reported. In this work, for the first time, polyvinylpyrrolidone (PVP) was used to level the sulfurization rate and reactivity of Cu and Co ions in a glycerol solution. As a result, the crystallographic growth direction of CuCo2S4 was controlled to be a sheet. Furthermore, the obtained CuCo2S4 nanosheets mainly exhibited an ultrathin thickness of approximately 15 nm. From the electrochemical measurements, the specific capacitance of the CuCo2S4 nanosheet was 1742 F g(-1) at a current density of 10 A g(-1). The capacitance retention was 93.4% at 10 A g(-1) for 2000 cycles. In addition, the CuCo2S4 nanosheet//rGO asymmetric supercapacitor exhibited an energy density of approximately 45.6 Wh kg(-1) at a power density of 748.2 W kg(-1). After 5000 cycles at a current density of 10 A g(-1), the capacitance retention was 91.7%.