Free-Standing, Flexible Carbon@MXene Films with Cross-Linked Mesoporous Structures toward Supercapacitors and Pressure Sensors

The preparation of multifunctional materials with low cost and simple synthesis processes is still challenging. Herein, by employing various sizes (50–500 nm) of polystyrene (PS) spheres as templates, different free-standing carbon@MXene films with three-dimensional (3D) mesoporous structures were fabricated through a simple multistep route. The microstructure, composition, mechanical property, conductivity, electrochemical activity, and sensing characteristics of these carbon@MXene films were investigated in detail. The intercalation of the PS spheres can effectively reduce the self-accumulation of MXene nanosheets and construct 3D cross-linked mesoporous structures, therefore broadening the ion transport channels and exposing more active sites of carbon@MXene films. When applied in a symmetrical supercapacitor, the optimized carbon@MXene electrode has a satisfactory specific capacitance of 447.67 F g–1 at a current density of 1 A g–1. Moreover, the 3D mesoporous structures of carbon@MXene films can significantly improve the sensitivity of the resultant pressure sensors with excellent stability (10,000 cycles). Thus, such mesoporous carbon@MXene films prepared by a facile yet robust route will be a versatile material for many applications.