Fluoride-Based Deep Eutectic Solvents with Amide Dual-Hydrogen-Bond Donors

Area of Science:

• Electrochemistry
• Materials Science
• Fluorine Chemistry

Background:

• Developing electrolytes with high fluoride ion (F-) concentration and stability is critical for electrochemical and chemical fluorination.
• Current F-DESs face challenges in balancing F- concentration and electrochemical stability.

Purpose of the Study:

• To synthesize and characterize novel fluoride-based deep eutectic solvents (F-DESs) using amide hydrogen-bond donors with dual N-H bonds.
• To evaluate the electrochemical properties, including concentration, electrochemical window, and ionic conductivity, of the synthesized F-DESs.

Main Methods:

• Synthesized F-DESs by mixing tetramethylammonium fluoride ([TMA]F) with 1,3-dimethylurea (1,3-DMU).
• Measured F- concentration, electrochemical window, and ionic conductivity at room temperature.
• Compared the properties of the new F-DES with existing ones using alcohol or thiourea hydrogen-bond donors.

Main Results:

• Achieved a high F- concentration of 2.6 mol dm-3 and a wide electrochemical window of 3.1 V with [TMA]F·3.5[1,3-DMU].
• The new F-DES exhibited a significantly wider electrochemical window (3.1 V) compared to an alcohol-based F-DES (1.9 V).
• Demonstrated ionic conductivity two orders of magnitude higher than a thiourea-based F-DES due to bifurcated hydrogen bonding.

Conclusions:

• The novel F-DES, [TMA]F·3.5[1,3-DMU], offers a promising combination of high F- concentration and electrochemical stability.
• The unique hydrogen bonding in 1,3-DMU enhances ionic conductivity, making it suitable for electrochemical fluorination.
• This study presents a new class of F-DESs for advanced fluorination technologies.