Three-dimensional hierarchical porous MXene aerogel with outstanding rate performance for flexible supercapacitors

Ti 3 C 2 T x MXene shows good promise in energy storage applications, but 2D MXene sheets exhibit serious stacking problems due to hydrogen bonding and van der Waals forces. This blocks active sites and impedes fast electrolyte ion transport. MXene pore structures can be designed to simultaneously inhibit interlayer stacking and accelerate ion transport. However, current studies on the pore structures of MXene are often limited to a single scale, meaning that the efficiency of electrolyte ion transport cannot be fully optimized. Therefore, inspired by nature, we designed a 3D hierarchical porous MXene that spans the microporous, mesoporous, and macroporous ranges. The constructed 3D hierarchical porous structure ensures the exposure of more active sites, shortens the paths available for electrolyte ion transport, and improves transportation efficiency. Thus, the performance of the MXene for electrochemical applications is comprehensively improved. As a supercapacitor electrode, the prepared Zn-H 2 O 2 -Ti 3 C 2 T x MXene exhibits good capacitance (378.8 F g −1 at 2 mV s −1 and 391.2 F g −1 at 1 A g −1 ) and superb rate performance (retention of 76.7 % at 1 V s −1 ). Moreover, this electrode can be stably cycled at 200 mV s −1 (10,000 cycles, retention of 95.88 %). At a power density of 120.8 W kg −1 , an assembled Zn-H 2 O 2 -Ti 3 C 2 T x /carbon cloth flexible symmetric supercapacitor exhibits an excellent energy density of 13.42 Wh kg −1 . This research offers new ideas for designing 3D hierarchical porous MXene materials.