Novel synthesis of B-doped Ti₃C₂T_x thin sheets via BF₃ Lewis acid etching: Structural insights and Supercapacitor applications

The rising demand for energy storage spurs research on supercapacitor materials, valued for high-power density and long-term cycling, vital in industries. Among two-dimensional materials, MXene, with a general formula of M_n+1X_nT_x, where M represents early transition metals, X indicates C and/or N, T_x represents functionalized surface groups, and n = 1, 2, or 3, stands out as an ideal candidate for energy storage applications. Here, for the first time, we report the use of a Lewis acid, boron trifluoride (BF₃), as an electron-deficient etchant in a sulfuric acid (H₂SO₄) solution for etching aluminum from the model system Ti₃AlC₂ MAX (M: transition metals, A: Al, X: carbon.), resulting in the formation of B-doped Ti₃C₂T_x MXene. Ex-Situ electrochemical X-ray diffraction (XRD) analysis showed reversible (002) plane changes in B-doped Ti₃C₂T_x MXene, from 5.72° to 7.0°, indicating ions intercalation and deintercalation, a first-time demonstration of significant ion transportation. Such fundamental insight determines that the specific capacitance of B-doped Ti₃C₂T_x MXene has found to be 396 F/g at current density of 1 A/g. This research introduces a novel synthesis approach aimed at understanding microstructural transformations of B-doped Ti₃C₂T_x MXene during electrochemical processes. This contributes to the advancement of MXene-based materials for future electrochemical applications.