A comprehensive investigation of multilayer Ti₃C₂Tₓ MXene for supercapacitors in alkaline and acidic media

Abstract

Multilayer Ti₃С₂T_x MXene was synthesized from Ti₃AlC₂ MAX phase via hydrofluoric acid etching followed by a gentle shaking-assisted delamination strategy, yielding well-preserved layered structures with expanded interlayer spacing of ~1.2–1.3 nm. Structural and spectroscopic analyses confirmed effective removal of Al layers and the formation of functionalized accordion-like MXene sheets. The electrochemical behavior was systematically investigated in symmetric two-electrode cells using alkaline and acidic electrolytes. The MXene electrode exhibited quasi-rectangular CV curves and symmetric charge–discharge profiles in alkaline media, indicating predominantly capacitive charge storage with good reversibility and rate capability. Significantly higher capacitance and improved retention were obtained in 6 M KOH, reaching ~70–72 F g^-1 at low scan rates, which is attributed to enhanced ionic conductivity, reduced charge-transfer resistance, and faster ion diffusion, as further supported by EIS analysis. In contrast, the acidic electrolyte showed distorted CV responses and increased polarization, suggesting slower charge-transfer kinetics and diffusion limitations. These findings highlight the decisive role of electrolyte chemistry in governing charge-storage mechanisms and demonstrate the strong potential of multilayer Ti₃С₂T_x MXene for supercapacitor applications in concentrated alkaline electrolytes.