By Steve Frandzel. Photo by Hannah O'Leary.
Kelsey Stoerzinger, assistant professor of chemical engineering, has been granted an award from the U.S. Department of Energy’s Early Career Research Program. She will use the five-year, $750,000 prize to develop a deeper understanding of electrochemical processes used to convert nitrate into ammonia, and to design and test catalysts that target this reaction.
Ammonia is among the most widely used chemicals in the world. But industrial-scale ammonia production relies on the Haber-Bosch process, in which hydrogen and nitrogen are combined at high temperatures and pressures. The practice requires enormous amounts of energy and produces huge volumes of carbon dioxide.
Meanwhile, nitrate from untreated wastewater and agricultural runoff overwhelms streams, rivers, and groundwater in many areas of the country. Ingesting excessive nitrate has been linked to a number of serious health risks in humans, while an overabundance in aquatic ecosystems can devastate plant and animal life.
Stoerzinger, who won an early career award from the National Science Foundation in 2021, will investigate an electrochemical option for ammonia synthesis in which an electric current is passed through a device containing nitrate-contaminated water. “We want to take this waste nitrate and transform it into a usable form, ammonia, and we’ll do that by applying electricity from renewable energy sources,” she said.
However, widespread implementation of an electrochemical approach will be feasible only with catalysts that select for, or favor, the reaction that produces ammonia rather than a competing reaction that produces hydrogen from the water molecules. Competing reactions can occur when the same starting materials combine to create undesired products.
Stoerzinger’s goal is to identify effective catalytic materials that result in high yields of ammonia. “Ideally, the catalyst should be highly selective for the nitrate-to-ammonia reaction and not for hydrogen production,” she said. “And it should be efficient, so that every electron flowing through the water creates ammonia, not hydrogen, even at low energy input.”
She intends to focus on materials made from abundant elements, like nickel, iron, and cobalt, because precious metal catalysts, while potentially useful, are too expensive for large-scale production. Stoerzinger will combine electrochemical studies, spectroscopy, and microkinetic modeling to gain a better understanding of how the electronic structure of catalysts determines competition between ammonia and hydrogen production under reaction conditions, thereby supporting the design of the most selective and efficient catalysts.
“We want to find sustainable solutions that allow us to recycle nitrate by upgrading it to something valuable,” Stoerzinger said. “Developing the most selective and efficient catalysts is the linchpin that will allow us to move the technology forward.”