Two Tufts Faculty Get Prestigious Award

Charles Sykes and Maria Flytzani-Stephanopoulos share the American Chemical Society Catalysis Lectureship for their groundbreaking research
single atoms of palladium visible on a copper surface
Individual palladium atoms visible on a copper surface. “This creates an opportunity for ‘green chemistry’,” said Maria Flytzani-Stephanopoulos. Photo: Charles Sykes
February 8, 2019

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We often use the word “catalyst” in conversation to point to something small that can have an enormous impact, sparking a movement, a transformation that goes well beyond the first, almost unnoticeable action.

In research that could have a large impact on a wide range of industries. Charles Sykes, professor of chemistry, and Maria Flytzani-Stephanopoulos, Robert and Marcy Haber Professor in Energy and Sustainability in the School of Engineering, have developed single-atom metal catalysts that could be significantly more efficient than those currently deployed in the production of goods such as fuel and plastics, the processing of food, and removing harmful gases in catalytic converters. The market for such catalysts is about $30 billion per year, and the catalysts are involved in the production of more than $10 trillion of goods annually.

Now Sykes’ and Flytzani-Stephanopoulos’ work has been recognized as they receive this year’s American Chemical Society Catalysis Lectureship, to be presented at the American Chemical Society national meeting in San Diego in August.

Charles SykesThe technology they developed is in the area of heterogeneous catalysis, which in this case means the catalyst is in solid form, and the reactants are gases or liquids. Their innovation is in the development of single-atom alloy catalysts, where catalytically active atoms, like platinum, palladium, or nickel are embedded in a solid matrix of a more inert metal, like copper. The active atoms are so dilute at the surface of the matrix—around one part in 100 —that chemicals only have the opportunity to interact with a single catalytic atom at a time.

That offers an advantage not only in the cost of catalysts themselves—metals like palladium are more expensive by weight than gold—but also in the chemistry. More densely packed catalysts can often be deactivated over time by the accumulation of unwanted compounds, similar to the way accumulation of soot can reduce the efficiency of an engine. The isolated atoms of the single-atom catalysts result in greater selectivity—the percentage of reactions that lead to wanted vs. unwanted products, as well as tolerance to deactivation.

Maria Flytzani-Stephanopoulos“This creates an opportunity for ‘green chemistry’,” said Flytzani-Stephanopoulos. “The reactions are cleaner, and the conditions can be milder,” reducing the need to include harsh reagents like mineral acids in the mix or the use of high temperatures that lead to the process having a larger carbon footprint.

The  single-atom alloy catalysts can be more easily studied using scanning tunneling microscopy and modeled by theory to understand their mechanisms than current industrial catalysts, which can have complex surface features and compositions. The Sykes Lab has used this approach to study their mechanism and refine their design, enabling a more rational process for the development of improved catalyst materials.

“This is a great example of collaboration between our chemistry department and the School of Engineering at Tufts,” said Sykes. “It’s a collaboration that has stretched over the last ten years, with students going back and forth between the departments to learn the language of each discipline and apply different techniques.”

Mike Silver can be reached at mike.silver@tufts.edu.