Tin+1Cn MXene with fully saturated and thermally stable Cl terminations

TL;DR

This paper demonstrates the synthesis of MXenes with fully saturated chlorine terminations that are thermally stable up to 750°C, expanding the functionalization options for MXenes and enabling new applications.

Contribution

It introduces a new surface termination for MXenes, chlorine, achieved through Lewis acidic melts, with detailed characterization and stability analysis.

Findings

Cl terminations are predominant on synthesized MXenes.

Cl terminations remain stable up to 750°C.

This new termination broadens MXenes' functionalization potential.

Abstract

MXenes are a rapidly growing family of 2D materials that exhibit a highly versatile structure and composition, allowing for significant tuning of the material properties. These properties are, however, ultimately limited by the surface terminations, which are typically a mixture of species, including F and O that are inherent to the MXene processing. Other and robust terminations are lacking. Here, we apply high-resolution scanning transmission electron microscopy (STEM), corresponding image simulations and first-principles calculations to investigate the surface terminations on MXenes synthesized from MAX phases through Lewis acidic melts. The results show that atomic Cl terminates the synthesized MXenes, with mere residual presence of other termination species. Furthermore, in situ STEM-electron energy loss spectroscopy (EELS) heating experiments show that the Cl terminations are stable up to 750 {\deg}C. Thus, we present an attractive new termination that widely expands the MXenes functionalization space and enable new applications.