Haozhe “Harry” Wang Receives NSF CAREER Award to Test the Limits of MXenes

Haozhe “Harry” Wang, assistant professor of electrical and computer engineering (ECE) at Duke University, has been awarded a National Science Foundation (NSF) Faculty Early Career Development (CAREER) Award.

The competitive five-year grant worth than $610,000 for outstanding young faculty will support Wang’s research as he explores the potential of a novel 2D class of materials known as MXenes (pronounced max-eens). A known pioneer in developing new methods for manufacturing materials with atomic-scale precision through both additive and subtractive processes.

MXenes, which were first created a little more than a decade ago, possess exceptional characteristics such as high electrical conductivity and strong photothermal capabilities to convert light into heat. Made of transition metals like titanium carbide, MXenes are only a few nanometers in thickness, equivalent to just a few layers of atoms. MXenes are used today in energy storage, desalination and soft robotics, but they hold great potential for more applications with improvements to the fabrication process.

The work associated with the grant will largely focus on two objectives, fabricating pure MXenes without defects and then characterizing those materials.

“We have a well-established method to produce MXene flakes, but we don’t know the limitations and full potential of the material,” Wang said. “Our goal is to investigate the intrinsic properties of MXenes and work toward fabricating a perfect and pristine material without defects. With a pure MXene, we can understand its theoretical limitations and potential applications.”

Currently, MXenes are typically made by soaking a metal compound powder in a strong acid, which removes interlayer atoms. Then, ultrasonic energy exfoliates the layered structures, leaving behind flakes, which are stacked to create thin films. This process produces high-quality materials, but they are not perfect. When working on the scale of individual atoms, it is extremely difficult to produce pristine MXene materials: The process may leave behind defects or unintentional functional groups on the surface that limit the material’s capabilities.

The alternative fabrication process Wang’s lab proposes is chemical vapor deposition, which uses gas and heat to grow a thin layer of MXenes in larger-sized flakes. Then, researchers can use a technique called atomic layer etching to remove or replace individual surface functional groups.

“If we can achieve as close to a pristine MXene as possible, we can easily imagine a significant enhancement in all related applications,” Wang said. “Maybe in the next 10 to 20 years, these understandings will turn into applications we can’t envision now. I am excited to work toward that future and explore the scientific and fundamental unknowns about MXenes that need to be answered first.”