Metal sites have been shown to impair the catalytic performance of SACs in some industrially important reactions, such as dehalogenation, CO oxidation and hydrogenation. An extensive range of metal ensemble catalysts have been devised to overcome such limitations.
Due to their high efficiency, the treatment of water holds enormous promise for catalysts consisting of only a few atoms. In a recent study, scientists explored how to improve the functionality of these catalysts and make them useful for practical use.
Nanoscale catalysts have gained a lot of interest in the field of water treatment in recent decades. Nanomaterials have a wide range of unique and useful properties. Recently, researchers have started exploring the possibilities of single-atom catalysts. These catalysts, which are much smaller than nanomaterials, can provide even more efficiency.
Because the materials commonly used for catalysts can be costly, efficiency is critical. For example, palladium (now sold for about $2,000 an ounce) is a metal often used in catalytic converters. A brief comparison explains why single-atom catalysts are so popular. Fifty nanometers of palladium costs about $37 to cover an area of about 250 square meters at the nanoscale. Only about 2% of its atoms are visible on the surface. In the form of one atom, palladium costs just 17 cents to cover an area the size of more than 50 football fields. And the efficiency is rated highly, with 100% atomic exposure on the surface.
Kim, the Henry P. Becton Sr. Professor of Chemical & Environmental Engineering, said: “Before, we didn’t have this capability, but now we’re basically loading metals from one atom, atom by atom, onto the substrate. And that’s great, because you can use all atoms.”
He said. “But they show properties more like a single atom because they’re such a small cluster and the atoms are all visible on the surface.”
He added. “Eventually we hope to have a very efficient device that has this catalyst to destroy pollutants in water because it will be so much cheaper and more efficient than other material designs.”
Scientists at the Yale School of Engineering and Applied Science have invented a method using a catalyst made of palladium atoms to reduce the carcinogen bromate in water. They added the nonmetallic elements sulfur, nitrogen and boron to the environment of the atomic ensembles. The overall results indicated that the catalytic performance of the system had improved. According to the researcher, it is a positive indicator, especially since water treatment must be as cost-effective as possible.
The limitation of single atom catalysts is that certain conditions can reduce their catalytic performance. As a remedy, researchers have started developing ensembles of catalysts, which are microscopic clusters of atoms. These clusters consist of only three or four atoms, as opposed to the thousands of atoms that make up a nanomaterial.
Researchers are still looking for the best ways to manage the properties of these ensemble structures and improve their performance because this material design is still relatively new. For example, the addition of specific elements around the metals can improve fully isolated single-atom catalysts. Kim and his team found that atom ensembles can be modified in the same way. Their paper is the first to explore the possibility.
The result shows that controlling the CE of SACs in an ensemble configuration is a potential technique for optimizing and enhancing their catalytic efficacy.
- Dahong Huang, Kali Rigby, et al. Enhancing the activity of Pd ensembles on graphene by manipulating the coordination environment. The National Academy of Sciences. DOI: 10.1073/pnas.2216879120