Oxidized-co-crumpled multiscale porous architectures of MXene for high performance supercapacitors

MXene, an example of two-dimensional (2D) transition metal carbides, is a promising electrode material for batteries and supercapacitors because of its excellent electrochemical properties derived from transition metal carbide/nitride constituents and its high electrical conductivity. However, similar to other 2D nanomaterials, MXene-based electrodes have a notable shortcoming of reduced specific surface area and reduced ion diffusion due to the self-restacking of MXene nanosheets. Here, to overcome these limitations, we present a novel method to create oxidized-co-crumpled multiscale porous architectures of MXene by a sequential process consisting of partial oxidation by hydrogen peroxide and then flocculation in acid. These treatments result in simultaneous generation of mesopores by oxidation and macropores caused by structural crumpling. This oxidized-co-crumpled MXene has a five times larger specific surface area (72 m2/g) than pristine MXene. In addition, the capacitance performance (307 F/g at 20 mV/s under 1 M H2SO4) and the capacitance at a higher scan rate (225 F/g at 100 mV/s) are improved. Additionally, after 6000 cycles, 87.6% of the capacitance is retained. Such an improvement in the properties is attributed to the structural advantages of the multiscale porous oxidized-co-crumpled MXene, wherein ion diffusion through mesopores is facilitated, while the crumpled macropores prevent re-stacking. Overall, this study demonstrates a promising strategy to create MXene-based high performance electrode materials for a variety of electrochemical applications.