Thickness-Independent Capacitive Performance of Holey Ti C T Film Prepared through a Mild Oxidation Strategy.

The Ti C T film with metallic conductivity and high pseudo-capacitance holds profound promise in flexible high-rate supercapacitors. However, the restacking of Ti C T sheets hinders ion access to thick film electrodes. Herein, a mild yet green route has been developed to partially oxidize Ti C T to TiO /Ti C T by introducing O  molecules during refluxing the Ti C T suspension. The subsequent etching away of these TiO  nanoparticles by HF leaves behind numerous in-plane nanopores on the Ti C T sheets. Electrochemical impedance spectroscopy shows that longer oxidation time of 40 min yields holey Ti C T (H-Ti C T ) with a much shorter relax time constant of 0.85 s at electrode thickness of 25 µm, which is 89 times smaller than that of the pristineTi C T film (75.58 s). Meanwhile, H-Ti C T film with 25 min oxidation exhibits less-dependent capacitive performance in film thickness range of 10-84 µm (1.63-6.41 mg cm ) and maintains around 60% capacitance as the current density increases from 1 to 50 A g . The findings clearly demonstrate that in-plane nanopores not only provide more electrochemically active sites, but also offer numerous pathways for rapid ion impregnation across the thick Ti C T film. The method reported herein would pave way for fabricating porous MXene materials toward high-rate flexible supercapacitor applications.