Surface Engineering of Ti₃C₂T_x MXenes via Silanol Functionalization for Improved Electrochemical Performance

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• MXenes, 2D transition metal carbides/nitrides, offer high conductivity and surface area for energy storage.
• Challenges include structural instability and limited cycling durability in MXene-based supercapacitors.

Purpose of the Study:

• To investigate covalent functionalization of Ti3C2Tx MXenes with 5,5'-bis(triisopropoxysilyl)-2,2'-bipyridine (BPS).
• To evaluate the impact of different solvents (m-xylene, ethanol, isopropanol) on functionalization efficacy and supercapacitor performance.
• To enhance the stability and cycling durability of MXene electrodes for supercapacitors.

Main Methods:

• Covalent functionalization of Ti3C2Tx MXenes with BPS in m-xylene, ethanol, and isopropanol.
• Characterization using X-ray photoelectron spectroscopy (XPS) to confirm BPS incorporation.
• Electrochemical testing of functionalized MXenes in asymmetric supercapacitors.

Main Results:

• XPS confirmed BPS incorporation, with m-xylene yielding effective functionalization without compromising charge transport.
• Ti3C2Tx-BPS (m-xylene) exhibited enhanced ionic conductivity (2.95 mS cm⁻¹) and H⁺ diffusion (4.08 × 10⁻¹² cm² s⁻¹).
• The asymmetric supercapacitor using Ti3C2Tx-BPS//activated carbon achieved high energy density (32.3 Wh kg⁻¹), power density (12,300 W kg⁻¹), and 88.36% capacitance retention after 15,000 cycles.

Conclusions:

• Solvent selection is critical for effective MXene functionalization.
• M-xylene mediated functionalization significantly improves the electrochemical performance and cycling stability of Ti3C2Tx MXenes.
• This approach offers a pathway for developing robust, high-performance MXene-based supercapacitors.