Golden Catalysts

July 24, 2018
Nanoscale model of a catalyst from Cynthia Friend's EFRC

How Cynthia Friend plans to revolutionize chemical production to lower energy costs worldwide

 

Imagine you give a child a push on a swing. She pumps her legs to gain momentum, but your push helps her accelerate.

A catalyst has a similar purpose: it can speed up a chemical reaction without being consumed by it. And, since 90 percent of all commercially produced chemical products involve catalysts during their manufacture, chances are good that the swing the child sits on, the snack she eats, her plastic toys, and the insulation in her house are all made with catalysts.

Chemical production, with or without catalysts, accounts for nearly 25 percent of energy use worldwide. What’s more, experts forecast that global energy demand will increase this number to 45 percent by 2040. Cynthia Friend, the T.W. Richards Professor of Chemistry, Professor of Materials Science, and Director of the Rowland Institute, wants to prevent this rise.

 

Rising prosperity lifts chemicals energy demand (Source: ExxonMobil)
(Source: ExxonMobil)

 

Now, with a multimillion dollar competing renewal grant from the U.S. Department of Energy (DOE), she’s well-positioned to “change the face and carbon footprint of the chemical industries sector,” one of her team’s goals. In 2014, the DOE’s Office of Basic Energy Science awarded Friend her first multimillion dollar grant to establish an Energy Frontier Research Center (EFRC). Her Center, titled Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC), set out to unravel how catalysis works and, consequently, to design better catalysts. 

Because catalysts need to function across a vast range of materials, temperatures, time, pressure, and more, they’re challenging to design. To tackle this challenge, Friend amassed an interdisciplinary team of experts in surface chemistry, theoretical physics, and machine learning from nine distinct institutions. Already, they’ve demonstrated the strength of their partnership. During the Center’s first four years, they published fifty-eight papers and discovered a way to transcend the trial-and-error approach to catalyst design.

With expertise from Tim Kaxiras, the John Hasbrouck Van Vleck Professor of Pure and Applied Physics, the team combined theoretical design with tightly-controlled experimental conditions. Computational models informed their experiments, and experimental results influenced model design. They relied on this cyclical method to—like an eddy—narrow in on improved designs.

But, Friend and collaborators wanted to do more than just make catalysts. They aimed “to predict catalytic behavior and to understand why we can predict it, not just to empirically predict but to understand the basis of it,” according to Friend. Their novel systematic approach, described in a paper in Nature Materials, yielded insights into how catalysts change just before, during, and after catalysis. As validation of this early work, other researchers have already adopted their approach to explore new materials and design enhanced catalysts.

 

NEW GOALS

The Center’s previous work could lead to more energy-efficient catalysts and chemical production, a feat itself. With their grant renewal, however, the team has a new focus: “selective catalysis.”

In production, chemical synthesis can create undesired byproducts, which can be unusable or dangerous. For example, oxidation processes—like those used in water treatment—can produce carbon dioxide and contribute to climate change. To subvert this, Friend and her collaborators intend to make these processes more selective, so that manufacturers produce more of what they want and less waste.

Catalysts could also help transform a noxious material, like methane, into a useful resource, like methanol. Fracking, for example, produces methane, which manufacturers often burn as a means of disposal. This only aggravates pollution. If, however, they could convert methane into methanol, they could then use this in new chemical synthesis or to produce fuel and solvents. They could, in effect, recycle their waste.

“If we can make any inroads in selectively transforming methane or propane to a useful chemical like methanol or related oxygen-containing molecules, it would be huge,” Friend said. She emphasizes, too, that understanding why something works is just as important. “That’s the goal in the next phase: to advance our ability to make quantitative predictions of selectivity. In other words, not to just qualitatively say something will get better or worse but how much better or worse if you change conditions.”

For their catalyst materials, the team has experimented with gold or silver combined with palladium. Gold and silver are stable elements that do not react easily and, therefore, can slow the reaction. Palladium reacts fast and can speed the process. With these so-called “bifunctional catalysts,” the team could achieve enough control over the reaction process to select which products—and byproducts—occur.

But these reactions also need a platform, like a stadium, to occur. According to Friend, the team is “trying to understand how to use the design of the catalyst material but also the reaction conditions to be able to basically drive the system to be much more selective.” For this aspect, Joanna Aizenberg, the Amy Smith Berylson Professor of Materials Science and Professor of Chemistry and Chemical Biology, together with a team at Lawrence Livermore Labs, designed nanoporous materials based on nature’s own catalyst platforms, like those in butterfly wings. These minuscule, porous scaffolds provide remarkable mechanical, thermal and chemical stability.

“The technology developed in my lab is particularly promising for bridging the gap between state-of-the-art R&D and real-world applications,” Aizenberg explained. “Due to its modular design and tunability, this framework can be used in various fields from the synthesis of important chemical products, to pollution abatement.”

 

CENTER OF COLLABORATION

Four years ago, Friend applied for an Energy Frontier Research Center in large part because of the opportunity to build an extensive collaborative network. “You can answer questions in a way that you couldn’t if you tried to do it individually,” she said of the group dynamic. “One of the gratifying aspects of having a Center like this is the range of people you get to interact with, the ideas they put out, and their ability to work together and go to new levels when they move to their next positions.”

Cynthia Friend and her EFRC Team
The IMASC Center hosts researchers and students from nine distinct institutions and myriad research backgrounds and offers a rare interdisciplinary and international space for collaboration and training. A select group are pictured above.

As of 2018, the Center hosts researchers from Harvard University, Tufts University, Lawrence Livermore National Laboratory, University of California Los Angeles, Berkeley Lab, Stony Brook University, University of Pennsylvania, University of Florida, and the University of Oslo. Students, in particular, thrive in such an interdisciplinary, international environment. For example, Michelle Louise Personick now occupies a faculty position at Wesleyan University and Branko Zugic is the Director of Chemical Engineering at L3 Open Water Power. Both Center veterans used the diverse skills they developed as a foundation to build successful careers.

Friend, who was recently elected into the American Academy of Arts and Sciences, attributes her recent successes to her team: “I have my colleagues to thank for that, too, because they’ve made it possible for us all to do things that were beyond what we could have done otherwise.”

Thus far, the prolific team has achieved advances in catalyst design that already impact how researchers approach this challenge. In their next phase, they aim to bring their theoretical designs closer to widespread application and use. If successful, they could indeed change the chemical industry into a more energy efficient, cleaner operation, worldwide.