Discovered in 2011, MXenes are a rapidly expanding family of ultrathin inorganic materials. They are made from a stack of transition metals combined with carbon or nitrogen, with atoms attached to their outer surfaces. These surface atoms are not just decorative. These play a central role in how the material behaves. “They have a strong influence on how electrons move through the material, how stable the material is, and how it interacts with light, heat, and the chemical environment,” explains Dr. Mahdi Ghorbani-Asl from the HZDR Ion Beam Physics and Materials Laboratory.
Until now, most MXenes have been manufactured using chemical etching. This process leaves a mixture of surface atoms such as oxygen, fluorine, and chlorine randomly scattered throughout the material. This lack of order creates problems. “This atomic disorder limits performance because it traps and scatters electrons, similar to potholes that slow down traffic on a highway,” explains Dr. Dongqi Li from the Dresden University of Technology.
Cleaner synthesis with precise surface control
A new technique known as the GLS method takes a completely different approach. Instead of relying on harsh chemicals, it starts with a solid material called the MAX phase and uses molten salt and iodine vapor to form MXene sheets. This process allows researchers to control which halogen atoms, such as chlorine, bromine, and iodine, attach to the surface.
The result is cleaner material. The surface atoms are uniformly and highly ordered, and unwanted impurities are greatly reduced. The team successfully generated MXenes from eight different MAX phases, demonstrating the versatility of this approach.
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 affect both stability and electronic behavior. “Combining theory with the experimental ability to precisely control surface termination opens new avenues for MXenes with improved stability and tailored functional properties,” concludes Ghorbani-Asl.
Dramatic improvement in conductivity and electron mobility
To highlight the impact of the new method, the team focused on one of the most widely studied examples: titanium carbide MXene Ti3C2. When manufactured using traditional techniques, this material typically contains a mixture of chlorine and oxygen on its surface, which interferes with its electrical performance. However, using the GLS method, the researchers created a version of Ti3C2Cl2 with only the chlorine atoms arranged in a clean, ordered structure and no detectable impurities.
“The results were surprising. The chlorine-terminated MXene variant showed a 160-fold increase in macroscopic conductivity and a 13-fold improvement in terahertz conductivity compared to the same material made by conventional methods. Additionally, we observed an almost four-fold increase in charge carrier mobility, an important measure of how freely electrons move through the material,” Li summarizes.
These improvements come directly from a smoother, more consistent surface. With fewer interruptions, electrons can move more freely through the material. Quantum transport simulations confirmed that the ordered structure reduces electron capture and scattering, providing a clear explanation for the observed performance enhancement.
Customize MXene for future technologies
Its benefits go beyond just conductivity. The study also shows that changing the type of halogen on the surface changes the interaction of MXene with electromagnetic waves. This enables the design of materials for specific applications, such as radar-absorbing coatings, electromagnetic shielding, and advanced wireless technologies. For example, chlorine-terminated MXene absorbs 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 further customization. By combining different halide salts, the researchers created MXenes containing two or three surface halogens in carefully controlled proportions. This ability to fine-tune surface composition provides powerful new ways to design materials for electronics, catalysis, energy storage, photonics, and other applications.
A major step forward in MXene chemistry
Overall, this work represents a significant advance in the field of MXenes. This introduces a gentler and widely applicable method for producing materials with highly ordered surfaces and precisely controlled chemistry. The researchers say this approach could accelerate the development of next-generation technologies such as flexible electronics, high-speed communication systems, and advanced optoelectronic devices.
