g-C3N4/MoO3 heterostructure decorated Ti3C2Tx MXene film as a flexible electrode for supercapacitors with high energy density and low temperature tolerance

The stackable and collapsible nature of MXene films results in a low volumetric energy density for supercapacitors (SCs) used in mini-portable electronic devices. Herein, a self-supporting carbon nitride (g-C3N4)/molybdenum trioxide (MoO3)-titanium carbide (Ti3C2Tx) MXene (CMM) hybrid film was prepared by vacuum filtration method. The electrochemical properties of the CMM hybrid electrode indicates that the incorporation of g-C3N4/MoO3 heterostructure can effectively enhance the specific capacitance of CMM, which exhibits good electrochemical performance in a wide temperature range from -20 to 40 degrees C. As expected, compared with the g-C3N4/Ti3C2Tx (402 F g(-1)), MoO3/Ti3C2Tx (625 F g(-1)), Ti3C2Tx (509 F g(-1)) electrodes, the optimal CMM electrode with 40 wt% g-C3N4/MoO3 exhibited a specific capacity of up to 1168 F g(-1) in 1 M H2SO4 electrolyte at 20 degrees C with a current density of 1 A g(-1). Moreover, it also shows satisfactory cyclic stability with capacitance retention of 96.8 % after 5000 cycles at 10 A g(-1). In addition, it demonstrates an energy density of 316 Wh kg(-1) and a power density of 1250 W kg(-1) at 20 degrees C when used as the electrode for button-type asymmetric SCs. Even at -20 degrees C, the CMM asymmetric SC presents an energy density of 230 Wh kg(-1), a capacitance retention of 81 % and coulombic efficiency of 92 % after 5000 cycles. Our work proposes a simple and effective method of incorporation g-C3N4/MoO3 heterostructure on MXene nanosheets to improve the stability of MXene in application of energy storage.