In situ Modified Mesoporous MXene Film with Excellent Oxidation Resistance for High-Performance Supercapacitor

In this paper, a simple and scalable process combining hydrothermal and etching was designed to prepare an in situ surface-modified mesoporous MXene, Ti₃C₂T_x, based on the synergistic effect of surface modification and mesoporous structure. It resulted that, the ion diffusion resistance was effectively reduced owing to the shortened ion diffusion pathway, and the pseudo-capacitance was significantly enhanced due to the increase of surface redox active sites by the modification of oxygen-containing groups. Meanwhile, the advantage of compact energy storage for Ti₃C₂T_x was retained. At the current density of 2 A g⁻¹, the volumetric capacitance reached 2079 F cm⁻³ (loading at 2.6 mg cm⁻²). As the current density increasing to 36 A g⁻¹, 83% (1732 F cm⁻³) of its initial volumetric capacitance was maintained showing excellent rate performance. In addition, the replacement of the fluorine group by the oxygen-containing group during the in-situ modification reduced the reduction state of the titanium element in Ti₃C₂T_x, achieving improved environmental stability. This work proposes a new strategy for MXenes to expand their potential application in the field of compact energy storage. At the same time, the suggested strategy based on "endogenous" modification is expected to provide new ideas to improve antioxidation ability of MXenes.