Water-Induced Local Redox Reactions on Individual Ti₃C₂T_x MXene Flakes in Aqueous Environment

Area of Science:

• Materials Science
• Surface Chemistry
• Electrochemistry

Background:

• Water confined in nanomaterials exhibits distinct properties compared to bulk water.
• Intercalated water in MXenes is hypothesized to influence surface chemistry and redox processes.
• The precise chemical interactions between confined water and MXene surfaces are not well understood.

Purpose of the Study:

• To investigate the in situ chemical interactions of water with individual Ti₃C₂T_x MXene flakes.
• To understand the effect of confined water on MXene surface chemistry and redox behavior.

Main Methods:

• Utilized scanning transmission X-ray microscopy (STXM) for high-resolution chemical imaging.
• Examined MXene flakes in both humid and aqueous environments.
• Analyzed the oxygen K-edge to probe water's hydrogen bonding and chemical state.

Main Results:

• Observed distinct hydrogen bonding patterns for water in MXene pockets/wrinkles versus interlayer spaces.
• Revealed water-induced, non-uniform local redox reactions of titanium atoms on the MXene surface.
• Demonstrated partial reversibility of these redox reactions with acidic electrolyte exposure.

Conclusions:

• Confined water significantly alters MXene surface chemistry through hydrogen bonding and redox reactions.
• These water-MXene interactions are crucial for understanding MXene's electrochemical performance.
• The findings provide insights into the role of water in 2D material electrochemistry.