Three distinct synthesis methodologies were developed and optimized: (1) traditional molten salt etching utilizing Ti₃AlC₂ MAX phase with ZnCl₂ at 550°C for 6 hours, producing Cl-terminated Ti₃C₂Clₓ MXenes; (2) ultra-fast low-temperature molten salt synthesis from Ti₂AlN and Ti₃AlC₂ MAX phase precursors employing bifluoride salts(NH₄HF₂ and KHF₂)/urea mixtures at 130°C-160°C requiring only 5-minute reaction times; and (3) in-situ HF etching of Al-rich MAX phases achieving high-concentration MXene dispersions of 5 - 50 mg/mL. Systematic parameter optimization encompassed reaction temperature, duration, precursor stoichiometry, and post-processing conditions.
Structural characterization via X-ray diffraction analysis confirmed successful MXene formation, with characteristic (002) reflections at ~7.7° 2θ and higher-order peaks indicating well-defined layered structures. Scanning electron microscopy and energy-dispersive spectroscopy analysis revealed morphological characteristics and elemental distribution consistent with successful aluminum etching and MXene formation.
Electrochemical evaluation demonstrated significant performance variations among synthesis routes. Al-rich MXenes synthesized at 1500°C exhibited superior electrical conductivity with current densities reaching 280 mA at 24 mg mass loading, substantially outperforming commercial MXene references. Resistivity measurements revealed values of 6.587 mΩ·cm for Al-rich MXenes compared to 1.037 mΩ·cm for commercial variants. The nitride-based Ti₂N MXenes presented unique delamination challenges, requiring modified lithium intercalation protocols for effective layer separation. Energy-dispersive spectroscopy confirmed varying surface termination compositions, with nitrogen content ranging from 29.6-58.9 atomic%, significantly influencing electrochemical behavior.
Stability assessments indicated sustained performance over extended cycling periods, with particular promise for applications in lithium metal anodes and energy storage systems. The chloride-terminated carbide MXenes demonstrated enhanced processability and electrochemical stability compared to nitride variants.
This systematic investigation establishes reproducible synthesis protocols for MXene materials and quantifies their electrochemical properties, providing fundamental insights for next-generation energy storage device development.