One-step hydrothermal preparation of a novel 2D MXene-based composite electrode material synergistically modified by CuS and carbon dots for supercapacitors

2D material MXene is one of the most interesting electrode materials due to its vast range of potential applications in electrochemical energy storage and conversion in recent years. Herein we fabricated a novel 2D MXene-based composite electrode material by using hydrothermally synthetized CuS and carbon dots (CDs) to synergistically decorate Ti3C2Tx. The introduction of CuS and CDs increases the interlayer spacing of Ti3C2Tx, which reduces the stacking of Ti3C2Tx unfavorable to the electrochemical performance. The optimal C-Ti3C2Tx/CuS composite electrode has an excellent specific capacitance of 1186 F·g−1 at a current density of 1 A·g−1, which is much higher than that of Ti3C2Tx samples decorated with single CuS or with single CDs, illustrating that CuS and CDs have the outstanding synergistic improvement effect to MXene on the electrochemical performance. When the current density rises to 10 A·g−1, the sample still maintains a capacitance of 907 F·g−1, corresponding to a capacitance retention rate of 76.5%. After 1000 cycles at a current density of 1 A·g−1, the capacitance remains 67% of the initial value. These demonstrate that the C-Ti3C2Tx/CuS composite electrode material has a great promising practical potential in fabricating high-performance supercapacitors. The new finding about the outstanding synergistic effect of CDs and transition metal compounds on improving MXene’s electrochemical performance suggests a possible effective way for preparing the high-performance MXene-based electrode materials. •Carbon dots was first adopted for improving the electrochemical properties of MXene.•One-step hydrothermal method was employed to simultaneously produce CuS and carbon dots.•The combination of CuS and carbon dots shows rare notable synergistic improvement effect to MXene.•The targeted C-Ti3C2Tx/CuS exhibits ultrahigh electrochemical capacitance performance.