BNL’s Stacchiola studies steps in producing hydrogen

BNL’s Stacchiola studies steps in producing hydrogen

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They know it works, but they’re not exactly sure how. They mix ingredients with something that helps make everything happen and, like a magician, wave their wand and get the rabbit, or in this case, the clean hydrogen, they were trying to produce. Except that, in their world, nature is the one whose slight of hand remains a mystery.

That’s where Argentinian-born Dario Stacchiola and his Brookhaven National Laboratory team of two postdoctoral researchers and one graduate student come in. An associate chemist, Stacchiola is trying to figure out the small steps in between the beginning of a reaction and the creation of this form of hydrogen, which is suitable for fuel cells in cars and industrial chemical processing.

While Stacchiola recognizes the possibility of a commercial use of his analysis down the road, he emphasizes that he is on a basic scientific mission. “Our end goal is not to get a commercial catalyst,” he said. “We are a step removed from that transition. We are really trying to look at the atomic level.”

Stacchiola’s curiosity about catalysts has earned him the admiration of his colleagues and coworkers. He is “well-respected not only across the lab, but also in our field,” said Ashleigh Baber, a postdoctoral researcher who has worked in his lab for three years.

His “knowledge of catalysis, coupled with his strength in experimental physical chemistry give him a unique perspective on how to approach and tackle important issues and holes in the field.”
Indeed, one of those many holes is understanding the intermediate reactions in the water-gas shift reaction, which is used to purify hydrogen and remove carbon monoxide.

“There are at least four different mechanisms proposed” for that reaction, Stacchiola said, with each one involving between five and 10 steps. His experiments helped to “narrow it down to two probable mechanisms.”

One of the big problems for scientists looking for these intermediate steps is that these reactions are easiest to see under cold, high-vacuum conditions, where the scientists don’t have to worry about interactions between the reactions they’re testing and atoms in the air. In those conditions, some of the intermediate chemicals generated during the reaction don’t form.

Using the latest technology, including near-ambient X-ray photoelectron spectroscopy, near-ambient pressure infrared reflection absorption spectroscopy, density functional theory computational analysis and scanning tunneling microscope, they were able to look behind the curtain in some of these steps at more everyday temperatures and pressures.

“We are now starting to see processes happen that we couldn’t see at lower pressures,” he said. He sees the stabilization of weak intermediates at the interface of oxide and metal nanoparticles in catalysts.

Scientists had predicted that the reactions Stacchiola studies would involve a carboxyl group, which is present in most organic acids and is made up of carbon, two oxygen atoms and hydrogen. These groups hadn’t been found on metal or oxide surfaces in this process. His research detected a product derived from the carboxyl group that was attached to the metal oxide interface of nanoparticles.

Scientists had predicted the likelihood of this carboxyl group for about a decade. The discovery of this combination of atoms was the closest thing to a “Eureka” moment he has had, Stacchiola said.

At conferences, Stacchiola has met with people who are trying to improve the efficiency of these reactions and who are looking to optimize the perimeter of oxide-metal interfaces.

Baber explained that “even small increases in catalytic efficiency extrapolate to huge savings in large-scale industrial processes.”
A resident of South Setauket, Stacchiola lives with his wife, Zulema Cabail, who does research and teaches microbiology at Stony Brook, and their 11-year-old daughter, Sofia, whose name, he said, is easy to reproduce in any language, which is helpful for a couple from Argentina who have lived in South America, Europe and North America.

As for his work, Stacchiola said he is driven by some of the same curiosities he had as a child, where he needed to understand how things worked. “I never felt very comfortable with black boxes,” he said.