Researchers at Washington University's McKelvey School of Engineering and the College of Engineering at Illinois at Chicago have developed a two-dimensional alloy material that is made of five metals, rather than the traditional two.It has also been demonstrated to be a catalyst for the reduction of CO2 into CO in a first for this material. This could have potential applications in environmental remediation.This research was done in the laboratory of Rohan Mishra (assistant professor in the Department of Mechanical Engineering & Materials Science, Washington University), and published in the journal Advanced Materials on Saturday, June 26.Mishra stated that they are looking into transforming carbon dioxide (a greenhouse gas) into carbon monoxide. Methanol can be made by combining carbon monoxide with hydrogen. This could be used to extract CO 2 from the atmosphere and then recycle it into a hydrocarbon.This innovation is based on a group of materials called transition metal dichalcogenides, (TMDCs). They include transition metals as well as a chalcogen that includes sulfur, selenium, and tellurium. An alloy that contains more than three metals in close equal amounts is called "high entropy." The material was named Mishra's laboratory high-entropy, transition metal dichalcogenides.TMDCs are not a new concept. Mishra stated that similar two-dimensional versions of these materials have been popular because of their unique electronic and optical properties. He had a feeling they could be used for another purpose.AdvertisementWe've been exploring their potential for electrocatalysis, acting as a catalyst to facilitate chemical reaction. They are two-dimensional, with three atoms thickness, making them efficient catalysts. Chemical reactions take place on the surface of materials, so a two-dimensional material has lots of surface area. The group published an earlier study in Advanced Materials in 2020 that showed that two-metal TMDC alloys had better catalytic activity than individual TMDCs. "This led to us asking the question: can these alloys be made even more efficient catalysts? Mishra agreed.There are 10 transition metals that can be used and 3 chalcogens. This means there are 135 and 756 possible TMDC allies. Not all combinations can be combined to make a homogenous mixture, much like oil and water.Mishra stated that without guidance from computations, it is difficult to determine which elements will make an alloy. This can lead to a costly and time-consuming trial-and-error process.John Cavin, a Washington University graduate student studying Physics in Arts & Sciences, was the alchemist in this instance.Cavin had previously shown that two transition metals can be combined and at what temperatures to create binary TMDCs alloys.Advertisement"The question was: "Could we even synthesize a TMDC alloy that contained that many components?" Cavin stated. Cavin said.He used quantum mechanical calculations for prediction of the combinations that would be most effective in increasing the material's capacity to catalyze CO 2. He needed to find out if the material was stable. However, he didn't have the tools. He developed it himself.Cavin stated that he had to create a thermodynamic model to predict stable, high-entropy TMDC alloys from quantum mechanical calculations. These calculations were made possible by the National Science Foundation's Extreme Science and Engineering Discovery Environment network. They used a lot of supercomputing resources.After many years of work, the analysis was finally sent to the University of Illinois at Chicago by experimental collaborators.Mishra stated that UIC could synthesize materials we had predicted would create a high-entropy TMDC alloy. "Furthermore one of them displayed exceptional activity."They could also be used for other purposes. UIC has synthesized three different TMDC alloys, and will continue to analyze them.Mishra stated that these are "new materials" and had never been synthesized before. They may possess unanticipated characteristics."This work is a result of a DMREF grant from National Science Foundation in the Materials Genome Initiative, which was launched by President Barack Obama as a multi-agency initiative that creates policy, resources, and infrastructure to support U.S. institutions in discovering, manufacturing, and deploying advanced materials cost-effectively and efficiently.
