Energy researchers discover fraction of an electron that drives catalysis

A team of researchers from the University of Minnesota Twin Cities College of Science and Engineering and the University of Houston’s Cullen College of Engineering has discovered and measured the fraction of an electron that makes catalytic manufacturing possible.

This discovery, published in the journal ACS Central Science, explains the utility of precious metals such as gold, silver and platinum for this manufacturing, and provides insight for designing new breakthrough catalytic materials.

Industrial catalysts—substances that reduce the amount of energy required for a given chemical reaction—allow producers to increase the yield, speed or efficiency of a specific reaction in pursuit of other materials. Such catalysts are used in processes related to pharmaceutical and battery production as well as petrochemical efforts such as the refining of crude oil, allowing supply to keep pace with demand in ways it otherwise could not.

Identifying faster and more controllable catalysts is a core goal of the multi-trillion-dollar fuels, chemicals and materials industries. In short, the world is currently in competition to produce faster, more efficient catalysts to enable lower-cost manufacturing processes across industries.

As molecules approach a catalyst surface, they share their electrons with the catalytic metal (in this case, gold, silver or platinum), thus stabilizing the molecules in such a way that the desired reactions occur. This concept has been theorized for over a century, but direct measurements of these tiny, highly consequential percentages of an electron have never been directly observed.

Researchers at the Center for Programmable Energy Catalysis, headquartered at the University of Minnesota, have now shown that electron sharing can be directly measured by a technique of their own invention called Isopotential Electron Titration (IET).

“Measuring fractions of an electron at these incredibly small scales provides the clearest view yet of the behavior of molecules on catalysts,” said Justin Hopkins, University of Minnesota chemical engineering Ph.D. student and lead author of the research study. “Historically, catalyst engineers relied on more indirect measurements at idealized conditions to understand molecules on surfaces. Instead, this new measurement method provides a tangible description of surface bonding at catalytically-relevant conditions.”

Determining the amount of electron transfer at a catalyst surface is key to understanding its performance. Molecules that are more prone to sharing their electrons bind stronger, with increasing reactivity, providing a directly measurable quantity for catalyst activity. Precious metals exhibit the precise extent of electron sharing with reacting molecules necessary to drive catalysis, even though this exchange has not been possible to directly measure until today.

IET can now serve as a tool for experimental description of new catalyst formulations, which will enable researchers to screen for and discover ideal catalytic substances more quickly going forward.

“IET allowed us to measure the fraction of an electron that is shared with a catalyst surface at levels even less than 1%, such as the case of a hydrogen atom on platinum,” said Omar Abdelrahman, corresponding author and an associate professor in University of Houston Cullen College of Engineering’s William A. Brookshire Department of Chemical and Biomolecular Engineering. “A hydrogen atom gives up only 0.2% of an electron when binding on platinum catalysts, but it’s that small percentage which makes it possible for hydrogen to react in industrial chemical manufacturing.”

With the emergence of nanotechnologies for synthesizing catalysts combined with new tools in machine learning to explore and utilize large datasets, engineers have identified large numbers of new catalytic materials. IET now enables a third method for directly characterizing new materials at a fundamental level.

“The foundation for new catalytic technologies for industry has always been fundamental basic research,” says Paul Dauenhauer, Distinguished Professor and director of the Center for Programmable Energy Catalysis at the University of Minnesota. “This new discovery of fractional electron distribution establishes an entirely new scientific foundation for understanding catalysts that we believe will drive new energy technologies over the next several decades.”