In situ oxidized Mo2CTx MXene film via electrochemical activation for smart electrochromic supercapacitors

Mo2CTx MXenes have great potential for multifunctional energy storage applications because of their outstanding electrical conductivity, superior cycling stability, and high optical transmittance. In this study, we fabricate Mo2CTx film electrodes (referred to as Mo2C) on fluorine-doped tin oxide (FTO) substrates using the layer-bylayer (LbL) self-assembly technique. To improve the energy-storage performance of Mo2CTx film electrodes, we develop a convenient electrochemical activation process to prepare in situ oxidized Mo2CTx/MoO3 film electrodes (referred to as EA-Mo2C). The Mo2CTx/MoO3 hybrid film benefits from the addition of MoO3, which introduces extra redox sites and enhances the charge-storage capacity. Furthermore, the unique layered structure of Mo2CTx significantly reduces the diffusion energy barrier for cations. The synergistic interaction between Mo2CTx and MoO3 results in superior electrochemical performance, and the EA-Mo2C displays a remarkable increase in areal specific capacitance, achieving 23.29 mF cm- 2 at a current density of 1.5 mA cm-2, which is 518 % higher than that of Mo2C. The electrochromic supercapacitor, assembled using EA-Mo2C as the ion-storage layer and polyaniline (PANI) as the electrochromic layer, enables power visualization and quantitative display. In summary, this study utilizes in situ electrochemical activation to derive high-performance electrode materials, offering an innovative strategy for advancing MXene-based energy-storage materials.