Ti3C2Tx/g-C3N4 heterostructure films with outstanding capacitance for flexible Solid-state supercapacitors

• Ti 3 C 2 T x /g-C 3 N 4 flexible free-standing electrode was prepared and show excellent performance. • Flexible solid-state supercapacitors were assembled and can work stably even in the 180° bending state. • DFT calculation was performed to reveal the mechanism of enhanced electrochemical performance of Ti 3 C 2 T x /g-C 3 N 4 heterostructure. With the popularity of intelligent portable electronic devices, bendable and flexible electronic equipment, such as portable miniature devices, wearable electronics, smart clothing, electronics, display, skin flexible smartphones and implantable medical devices have become a development trend. As potential energy storage device, flexible supercapacitors have attracted extensive attention. Ti 3 C 2 T x MXenes, which has high capacitance, mechanical strength and flexibility, perfectly meets the requirements of flexible energy storage devices. In order to avoid stacking, increase layer spacing, and enhance charge transfer efficiency, the Ti 3 C 2 T x /g-C 3 N 4 heterostructure is constructed by self-assembly method. The flexible self-supporting electrode is prepared by vacuum assisted filtration, which successfully widen the potential window and significantly improve the capacitance performance. The specific capacitance of the electrode in 1 M H 2 SO 4 electrolyte reaches 414 F/g at 1A/g. The electrode can simultaneously act as a fluid collector to construct a simple ultra-thin device. The flexible all-solid symmetric supercapacitor is assembled and the energy density reaches 23.98 Wh/Kg when the power density is 139.66 W/Kg. Encouragingly, the device can maintain stable performance under 180° bending conditions. The above excellent performance confirms the applicability of supercapacitors based on Ti 3 C 2 T x /g-C 3 N 4 heterostructure films for future portable, flexible or wearable electronic energy storage devices.