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Institute for Integrated Catalysis

Embracing Complexity and Chaos: Roger Rousseau

An expansive, realistic attitude to molecular theory garners novel findings, talented cadre of scientists

Roger Rousseau
Roger Rousseau's expansive, realistic attitude about molecular theory has produced novel findings about catalysts and the associated reactions.

What you see in the details says something about your personality and your job. For those who create and use computer models to understand the fundamental laws of the universe, details are what ground models in reality.

"You can't simplify it too much and still get novel answers," said Dr. Roger Rousseau, whose work has pushed state-of-the-art theory into solving increasingly harder problems at Pacific Northwest National Laboratory (PNNL). "We capture the complexity of the systems—that means a lot of atoms, energetics, and kinetics." Instead of working with a well-defined model and forcing it to match reality, Rousseau and his colleagues work with models that attempt to reflect complex problems and then solve them.

The Complexity of Catalysts

Embracing real-world complexity to accurately simulate molecules, solids, and surfaces has led Rousseau and his colleagues to make novel discoveries. For decades, scientists could not definitively resolve how much energy was needed to split water molecules on the surface of a titanium dioxide catalyst. The answer would inform them about other systems where breaking bonds is crucial, such as synthesizing biofuels or storing carbon. "The problem wasn't that there wasn't enough data," said Rousseau. "Everyone had tons of answers. They just weren't what we needed."

Conventional instruments couldn't measure water's stability, or the amount of energy needed to make water molecules fall apart. Because an instrument able to measure the energy and record the collisions didn't exist, the team built what they needed. The resulting instrument resides in DOE's EMSL. By iterating between experiments, led by Dr. Zdenek Dohnálek at PNNL, and calculations and simulations, led by Rousseau and his colleagues, they discovered that when the water fragmented to form two hydroxyl groups, the amount of energy needed to activate the bond that splits off the proton is relatively small, just 0.36 eV. The amount of energy to put the water back together is only 0.035 eV smaller.

"The truly novel thing was that the oxide surface influences the water molecules from relatively far away (several molecular lengths in this case)," said Rousseau. This influence allowed the oxide to steer the molecule into the exact orientation to snap the hydroxyl bond when it hit the oxide surface. While such molecular steering is seen on metal surfaces, it occurs at much shorter distances. "When I saw the data, it hit me that this can only be explained by looking at how the water molecules approach the surface," said Dr. Vanda Glezakou, who suggested this analysis.

"Instead of working with a well-defined model and forcing it to match reality, we work with models that attempt to reflect the complexity of reality and solve them." Roger Rousseau

This was far from obvious to the other team members. But working as part of the team that Rousseau put together means speaking up, even when it contradicted every reasonable expectation of what an oxide should do. "Roger's attitude is 'don't tell me what I want to hear, tell me the truth,'" said Glezakou.

The resulting article, published in the Proceedings of the National Academy of Sciences USA, is just one example from a diverse portfolio of catalysis and energy research. For example, the team spent more than a year examining oxygen atoms—the anchor points for catalysts on graphene surfaces. Understanding where oxygen rests is vital for understanding how other materials can be anchored on graphene to make the next generation of catalysts.

By again combining computational chemistry with theory, Rousseau, Dohnálek, Glezakou, and the other team members discovered that single oxygen atoms bind to graphene supports in an unexpected way. On a graphene sheet set atop ruthenium metal, single oxygen atoms bind to a single carbon atoms. Moreover, because the graphene sheet buckles on the metal, these oxygen atoms appear in predictable spots.

These examples are just part of Rousseau's research portfolio. He's maintained a philosophy throughout his career to go for the interesting problems, regardless of the challenges. For example, with the Center for Molecular Electrocatalysis, a DOE Office of Science Energy Frontier Research Center, he's shown how computer models can map out every step in the complicated mechanism of producing hydrogen fuel.

"He's pushing the forefront of using modeling to understand experimental studies. He tailors the complexity of the model based on the depth of understanding needed," said Dr. Wendy Shaw, who leads the Physical Sciences Division at PNNL and serves as Rousseau's manager.

It Takes a Village

Doing this kind of research takes a team, Rousseau is quick to point out. "If I was doing purely fundamental work, I could define a space and be the expert, but I'm working in a technology area [catalysis] that requires non-incremental changes," said Rousseau. "The projects are simply too big for any one individual to do. Solving the problems requires a diverse group of people with different expertise."

This desire to bring together differing viewpoints and experiences can be readily seen in the symposiums and events Rousseau has helped organize. For example, in 2011, he co-organized an American Chemical Society symposium that bridged the various divides in catalysis. The symposium covered molecular and heterogeneous catalysis, theory and experimentation, and fundamental science and applied research in biofuels, batteries, and other energy sources.

"To drive the field forward, we need all of these perspectives," said Rousseau.

Team members
Hiring and mentoring a diverse group is a vital part of Roger Rousseau's job; his efforts have resulted in a team with a broad background and deep expertise in theory and fundamental science.

Hiring a diverse group is part of Rousseau's job as the lead of PNNL's Basic and Applied Molecular Foundations group. "Our broad background and deep expertise in theory and fundamental science make us stand out in the catalysis community. We get the breadth because we pull together multiple disciplines and the depth because of the expertise we have."

Building and maintaining that expertise requires recruiting people and building their careers. The first part is tricky, but the second requires dedication and compassion. "Roger really invests in the people that work for him," said Shaw. "He really cares about the people that work for him and invests in their careers."

In a move that some would claim is unusual, Rousseau's career development and mentoring efforts have continued even after the scientists have left PNNL. He is that person you can call for advice and recommendations long after you've stopped working on the same project or for the same institution.

The success of this team and the multidisciplinary approach combined with complicated models has created a high-quality environment that bridges the fundamental side of the house (physical and computational sciences) and the technology side (applied energy and environmental work). "I don't know many people that combine Roger's intellect, work ethic, kindness, genuine interest in growing people and total disregard for rest," said Glezakou. "Top all this with a wicked sense of humor."

Building Trust, Finding Answers

Having experienced the difference between horrid and exceptional leadership on several continents, he chose to adopt the practices of the excellent role models he encountered. Rousseau is very conscious of what it takes to build engaged, creative teams. He believes in a fluid structure to encourage communication and ownership. His philosophy is simple: Everybody owns the deliverables and everybody works toward it. This concept started forming even as he was mentoring students and colleagues while getting his graduate degree from the University of Michigan. He kept on doing mentoring through research studies and positions in Spain, Germany, Canada, and Italy, but being a professor wasn't a path he wanted to follow. "The traditional academic route just didn't appeal to me," he said.

"I had the opportunity to take a safer route, but I chose to work with Dr. Michele Parrinello in a completely different field," Rousseau said. Throughout his career, he's followed his interests and the opportunity to learn. This has led him to leadership roles in both PNNL's Institute for Integrated Catalysis and the Chemical Transformations Initiative. "I've changed the type of things I've done four or five times in my career. I started in synthetic chemistry, moved on to theory, physics and high-performance computing, and back to theoretical chemistry," said Rousseau. "It hasn't been safe, but it hasn't been boring!"

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