Scientists Grow MXene Crystals Directly From Gas, Opening Path to Cheaper Electronics

Fifteen years after they were first synthesized in a laboratory at Drexel University, MXenes remain one of the most celebrated families of two-dimensional nanomaterials in modern chemistry, praised by the International Union of Pure and Applied Chemistry as an emerging technology with true potential to transform the world. Yet despite dazzling demonstrations in energy storage, water filtration, and electromagnetic shielding, MXenes have struggled to escape the confines of specialized laboratories. The bottleneck has never been a lack of ideas for using them; it has been the complicated, costly, and waste-intensive process required to make them. Now, a team of researchers led by Drexel University, working with collaborators at the University of Pennsylvania and Murata Manufacturing Co., Ltd., reports a decisive step toward industrial-scale MXene production through a gas-phase route that bypasses nearly every burdensome step of the traditional method.

The conventional way of making MXenes reads like a chain of laboratory chores. It begins with a precursor called a MAX phase, a layered ceramic powder that must itself be synthesized. That powder is then combined with a liquid etchant, most commonly hydrofluoric acid, agitated repeatedly, washed, and spun in a centrifuge multiple times to strip away the reaction byproducts. What emerges is MXene material in a form that still demands further processing into an ink, a coating, or a film before it can be put to work. Each of these stages adds cost and time, and the wet chemical etching generates toxic waste while potentially leaving flaws on the surfaces of the delicate flakes. Although the process has been tuned to yield a wide range of chemical compositions and scaled to kilograms per day, its dependence on a separately synthesized precursor has remained a fundamental constraint.

Yury Gogotsi, distinguished university and Bach chair professor in Drexel’s Nick Howley College of Engineering and Computing and one of the discoverers of MXenes, led the new study, published in the Journal of the American Chemical Society. Being able to combine a solid metal source with abundant and inexpensive gaseous reactants to form MXenes directly, he explained, opens a fundamentally different manufacturing pathway. The approach builds on a vapor-phase deposition process pioneered by researchers at the University of Chicago, who reported the first chemical vapor deposition synthesis of MXene, but it introduces markedly cheaper starting materials: titanium tetrachloride, an industrial commodity already produced in enormous quantities to make titania, the white pigment found in paint and sunblock, and methane, the principal component of natural gas.

The experimental recipe is disarmingly simple compared with its wet-chemical rival. The researchers placed titanium powder in a quartz carrier tube, introduced methane, and heated the mixture in a conventional tube furnace to trigger the reaction. As the hot gaseous mixture cooled, a layer of crystalline MXene, specifically the compound Ti2CCl2, formed on the quartz substrate. No MAX phase synthesis preceded the reaction, and no acid etching followed it. Hyunho Kim, a research professor at Sungkyunkwan University in South Korea and first author of the paper, who conducted the research as a postdoctoral assistant in Gogotsi’s laboratory, emphasized that growing crystalline MXene directly from abundant precursors, without first making and etching extra precursor materials, represents a significant development. MXene inks made by selective etching, he noted, remain valuable for coatings and printed devices, while vapor-phase synthesis offers a complementary route to crystals with extremely low defect density for future electronics, optics, and quantum technologies.

Beyond simplifying the supply chain, the team discovered that they could exert meaningful control over the material by manipulating the geometry of the reaction itself. By increasing the exposed surface area of the titanium and confining the reaction within a narrow carrier tube, they found that MXene formed on the quartz substrate without ever making direct contact with the solid titanium source. Under these confined conditions, the material self-organized into rounded structures known as spherulites, which together formed a porous nanocrystal network. The confined space, the researchers concluded, drives saturation of titanium chloride vapor to the level required for two-dimensional crystal growth, a key chemical mechanism that explains why the process works and how it might be tuned.

Time proved to be another powerful dial. As the synthesis proceeded for longer periods, the researchers observed continuous lateral growth into larger flakes. Individual spherulites expanded outward and merged with their neighbors, producing swirl-like crystalline domains containing individual flakes tens of micrometers across. This behavior demonstrates that crystalline two-dimensional MXene can be synthesized directly through a gas-to-solid growth process, and the sustained lateral expansion hints at something even more ambitious: the feasibility of producing large-area, and eventually wafer-scale, MXene crystals using equipment and principles familiar to the semiconductor industry.

The industrial logic of the process may prove to be its most compelling feature. Gogotsi pointed out that the new method shares important similarities with the chloride route used for industrial titania production. Both rely on titanium tetrachloride as a high-temperature vapor precursor; conceptually, methane supplies the carbon in the MXene process just as oxygen is used to form titania. Because titanium chloride is already handled at a very large industrial scale to produce millions of tons of titania each year, the same engineering principles could ultimately be adapted to produce inexpensive MXene powder in ton-scale quantities. For a material whose commercial adoption has been throttled by manufacturing complexity, that parallel to one of chemistry’s largest commodity processes is a striking endorsement of scalability.

Cost reduction extended to the metal source as well. Whereas the original University of Chicago study used high-purity titanium foil as its starting material, the Drexel-led group sourced its precursor from titanium sponge, an abundant industrial product that is substantially less expensive than high-purity titanium. Combined with the elimination of the MAX phase synthesis and the acid-etching steps, along with their associated toxic waste streams, the economics of MXene production begin to look radically different. Fewer steps mean fewer opportunities for contamination and defects, and gaseous precursors lend themselves to the kind of continuous, controlled manufacturing that has made electronic-grade materials affordable at scale.

The implications reach well beyond cheaper powders. According to the researchers, continued control over nucleation and lateral growth could eventually enable large-area, low-defect MXene crystals and even wafer-scale conducting films suitable for electronics, optical communication, and quantum computing. Crystalline films grown directly from the vapor phase, with their extremely low defect densities, are precisely the form factor demanded by next-generation devices, where flake boundaries and surface imperfections degrade performance. A route that grows such crystals directly on a substrate, from commodity chemicals, in a conventional tube furnace, positions MXenes to compete with established two-dimensional materials on the manufacturing terms that matter most.

Challenges remain before MXenes move from the quartz tube to the factory floor. The next phase of the research will focus on refining the process to ensure structural uniformity, increasing flake size, and achieving precise control over the surface chemistry of the resulting materials, which governs how MXenes conduct charge and interact with their environment. The team also intends to adapt the process to produce MXenes with other chemical compositions, broadening the palette of properties available to device designers. Still, the demonstration that a material born in an acid flask can now be grown as a crystalline film from natural gas and a paint pigment precursor marks a turning point. The discovery of a key chemical mechanism for scalable vapor-phase growth suggests that the barriers that have kept MXenes in the laboratory for a decade and a half may finally be dissolving, one wafer at a time.

Subject of Research: Vapor-phase chemical synthesis of two-dimensional Ti2CCl2 MXene crystals for scalable industrial production

Article Title: New process for making MXenes via vapor-phase synthesis could expand technological applications

Article References: New process for making MXenes via vapor-phase synthesis could expand technological applications. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: MXenes, two-dimensional materials, chemical vapor deposition, titanium tetrachloride, nanomaterials, Drexel University, energy storage, quantum computing, materials science, Ti2CCl2, thin films, industrial manufacturing