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.