Termination-Property Coupling via Reversible Oxygen Functionalization of MXenes

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• MXenes (2D transition-metal carbides/nitrides) show great application potential.
• Surface termination significantly impacts MXene properties, but experimental control is challenging.

Purpose of the Study:

• To develop an effective method for controlling MXene surface termination, specifically increasing oxygen functionalization.
• To investigate the impact of enhanced oxygen functionalization on MXene properties.

Main Methods:

• Annealing MXenes (Ti2CTx and Mo2TiC2Tx) in an argon-oxygen (Ar + O2) low-power plasma.
• Characterizing the resulting surface termination and material properties.
• Investigating reversible alteration of oxygen content via vacuum and plasma annealing.

Main Results:

• Plasma annealing successfully increased oxygen (=O) functionalization on MXenes with minimal secondary phase formation.
• Increased oxygen content led to higher electrical resistance and decreased surface transition-metal electron counts.
• Reversible control of oxygen content was demonstrated for Mo2TiC2Ox.

Conclusions:

• Plasma annealing offers an effective route to tune MXene surface functionalization.
• Controlled surface termination can unlock novel, surface-dependent MXene properties.
• This method provides a pathway for designing MXenes with tailored functionalities.