Synthesis of Chlorine-Terminated MXenes by Dry Selective Extraction with TiCl₄.

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• MXenes are a promising class of nanomaterials with diverse applications.
• Scalable synthesis and surface chemistry control remain key challenges for MXene development.
• Current wet-chemical and molten salt etching methods require extensive post-processing.

Purpose of the Study:

• To develop a novel, scalable dry etching method for MXene synthesis.
• To achieve uniform halogen surface terminations on MXenes.
• To explore the properties and potential applications of the synthesized MXenes.

Main Methods:

• Utilized titanium tetrachloride (TiCl4) as a gas-phase etchant for selective aluminum (Al) extraction from MAX phases.
• Employed computational analysis to understand the reaction mechanism between TiCl4 and MAX phases.
• Delaminated the resulting Ti3C2Cl2 MXene using lithium ion intercalation in an organic solvent.
• Investigated the self-assembly behavior of delaminated MXene flakes.

Main Results:

• Demonstrated TiCl4 as an effective dry etchant for producing chlorine-terminated MXenes.
• Showed that TiCl4 directly extracts AlCl3 without intermediate phases.
• Successfully delaminated Ti3C2Cl2 into few-layer flakes.
• Observed the formation of 1D nanoscrolls from hydrophobic delaminated flakes.
• Established a scalable synthesis route for halogen-terminated Ti- and Nb-based MXenes.

Conclusions:

• The developed dry etching process offers a scalable and efficient route for MXene production.
• Uniform chlorine terminations enable controlled surface chemistry, opening avenues for tailored material properties.
• The formation of nanoscrolls suggests potential for novel applications in areas like energy storage and electronics.