Novel fabrication technique takes transition metal telluride nanosheets from laboratory to mass production

Transition metal telluride nanosheets have shown enormous promise for basic research and other applications across a rainbow of fields, but until now, mass fabrication has been impossible, making it more of a laboratory curiosity than an industrial reality.

But a team of researchers recently developed a novel fabrication technique—using chemical solutions to peel thin layers from their parent compounds, creating atomically thin sheets—that seems to finally deliver on the promise of ultra-thin materials.

The researchers describe their fabrication technique in a study Published Inside Nature.

The world's thinnest or 'two-dimensional' materials—consisting of a single layer of atoms—transition metal telluride (TMT) nanosheets have, in recent years, generated great excitement among chemists and materials scientists for their extraordinary properties. .

These compounds, composed of tellurium and any element in the 'middle' of the periodic table (groups 3-12), enjoy a range of states from semi-metallic to semiconducting, insulating and superconducting and even more exotic states. as well as magnetic and unique catalytic activity.

These properties offer a range of potential applications across electronics, energy storage, catalysis and sensing. In particular, DMT nanosheets are being explored as new electrode materials in batteries and supercapacitors, which are essential for clean conversion due to their high conductivity and large surface area.

TMT nanosheets can also be used as electrocatalysts for lithium-oxygen batteries, improving their performance and efficiency. Other potential applications in emerging technologies include photovoltaics and thermoelectrics, hydrogen production, and filtration and separation. They have also been found to exhibit interesting quantum phenomena such as quantum oscillations and giant magnetoresistance.

„The list of industries that will experience significant efficiency improvements from the mass production of DMT nanosheets is very long,” said team leader WU Zhong-Shuai, a chemist at the Dalian Institute of Chemical Physics (DICP), Chinese Academy of Sciences. „That's why this 2D object is so exciting.”

Unfortunately, despite various attempts to exfoliate high-quality TMT nanosheets, preserving high crystallinity while achieving large nanosheet size and ultrathin aspect ratio remains a significant challenge. The methods designed so far are not scalable due to long processing times. They often require toxic chemicals. Therefore, the properties of TMT nanosheets remain an interesting laboratory phenomenon that cannot progress to mass production and industrial application.

The team finally overcame this problem with a simplified process of lithiation, hydrolysis, and finally, nanosheet exfoliation.

First, large-scale metal telluride crystals were produced using chemical vapor transport—a technique commonly used in chemistry to transport solid compounds from one place to another using a carrier gas. As the reaction vessel is heated, the transport agent vaporizes, carrying the solid mixture with it as a vapor.

The vapor travels through the reaction vessel and may encounter a cold surface where the compound may form crystals. This allows controlled growth of crystals or very thin films of the desired composition. In this case, the prepared telluride crystals are then mixed with lithium borohydride. The process involves depositing lithium ions between layers of metal telluride crystals, leading to the formation of an intermediate, 'lithiate' compound.

The lithiated intermediate compound is then quickly soaked in water, resulting in „exfoliation” or removal of the lithiated metal telluride crystals into nanosheets in seconds.

Finally, the exfoliated metal telluride nanosheets are collected and characterized based on their shape and size, allowing them to be processed into various forms such as films, inks, and composites depending on the desired application.

The entire process takes tens of minutes for lithiation and seconds for hydrolysis. This technique is capable of producing high-quality TMT nanosheets of various desired thicknesses with very high yields.

When the nanosheets were tested, the researchers found that their charge storage, high-rate capacity, and stability showed promise for applications in lithium batteries and micro-supercapacitors.

They believe their technique is essentially ready for commercialization, but want to conduct further studies to characterize the properties and behavior of their nanosheets, as well as to further refine and optimize the lithiation and exfoliation stages.