Discovered in 2011, MXenes are a fast-expanding family of ultra-thin inorganic materials. They are made from stacked layers of transition metals combined with carbon or nitrogen, with atoms attached to their outer surfaces. These surface atoms are not just decorative. They play a central role in how the material behaves. “They strongly influence how electrons move through the material, how stable it is, and how it interacts with light, heat, and chemical environments,” explains Dr. Mahdi Ghorbani-Asl from the Institute of Ion Beam Physics and Materials Research at HZDR.
Until now, most MXenes have been produced using chemical etching, a process that leaves a mix of surface atoms such as oxygen, fluorine, or chlorine scattered randomly across the material. This lack of order creates problems. “This atomic disorder limits performance because it traps and scatters electrons, much like potholes slowing traffic on a highway,” describes Dr. Dongqi Li from TU Dresden.
Cleaner Synthesis With Precise Surface Control
A new technique known as the GLS method takes a very different approach. Instead of relying on harsh chemicals, it starts with solid materials called MAX phases and uses molten salts along with iodine vapor to form MXene sheets. This process allows researchers to control which halogen atoms, including chlorine, bromine, or iodine, attach to the surface.
The result is a much cleaner material. The surface atoms are arranged in a uniform and highly ordered way, and unwanted impurities are greatly reduced. The team demonstrated the versatility of this approach by successfully producing MXenes from eight different MAX phases.
To better understand how these surface changes affect performance, the researchers also used density functional theory (DFT) calculations. These simulations provided detailed insight into how different surface terminations influence both stability and electronic behavior. “By combining theory with our experimental ability to precisely control surface terminations, we open a new path toward MXenes with improved stability and tailored functional properties,” concludes Ghorbani-Asl.
Dramatic Gains in Conductivity and Electron Mobility
To highlight the impact of the new method, the team focused on titanium carbide MXene Ti3C2, one of the most widely studied examples. When produced using conventional techniques, this material typically contains a mix of chlorine and oxygen on its surface, which interferes with its electrical performance. With the GLS method, however, the researchers created Ti3C2Cl2, a version with only chlorine atoms arranged in a clean, ordered structure and no detectable impurities.
“The results were striking. The chlorine-terminated MXene variant showed a 160-fold increase in macroscopic conductivity and a 13-fold enhancement in terahertz conductivity compared with the same material made by traditional methods. In addition, a nearly fourfold increase in charge carrier mobility was observed, a key measure of how freely electrons move through a material,” Li summarizes.
These improvements come directly from the smoother, more consistent surface. With fewer disruptions, electrons can travel more freely across the material. Quantum transport simulations confirmed that the ordered structure reduces electron trapping and scattering, offering a clear explanation for the observed performance boost.
Customizing MXenes for Future Technologies
The benefits go beyond electrical conductivity. The study also shows that changing the type of halogen on the surface alters how MXenes interact with electromagnetic waves. This makes it possible to design materials for specific uses, including radar-absorbing coatings, electromagnetic shielding, and advanced wireless technologies. For instance, chlorine-terminated MXenes absorb strongly in the 14-18 GHz range, while bromine- and iodine-based versions respond to different frequency ranges.
The GLS method also opens the door to even more customization. By combining different halide salts, researchers created MXenes with two or even three types of surface halogens in carefully controlled proportions. This ability to fine-tune surface composition provides a powerful new way to design materials for electronics, catalysis, energy storage, photonics, and other applications.
A Major Step Forward for MXene Chemistry
Overall, this work marks an important advance in the field of MXenes. It introduces a gentler and widely applicable way to produce materials with highly ordered surfaces and precisely controlled chemistry. According to the researchers, this approach could speed up the development of next-generation technologies, including flexible electronics, high-speed communication systems, and advanced optoelectronic devices.
