CAS-SC: Elucidating the Electrocatalytic Coupling of Nitrate and Carbon Dioxide: Toward Electron Efficient C-N Coupling

With the support of the Chemical Catalysis Program in the Division of Chemistry, Nirala Singh, Bryan Goldsmith, and Suljo Linic of the University of Michigan are studying the production of urea, an important fertilizer, using renewable electricity, carbon dioxide, and nitrate from wastewater. Urea is currently manufactured using ammonia. Ammonia production for urea synthesis emits large quantities of carbon dioxide because ammonia is produced by first converting natural gas to hydrogen and carbon dioxide, then combining hydrogen and nitrogen at high temperatures. The proposed process will instead use low-temperature electrochemical methods powered by renewable electricity to couple carbon dioxide and nitrate to directly produce urea with much less carbon dioxide emissions. This research has the potential for a paradigm shift in the production of urea while mitigating two harmful air and water pollutants. The project will engage elementary schoolers about STEM (science, technology, engineering and mathematics) through the Grizzly Scholar program and provide high school students with research experience each summer through a Summer High School Apprentice Researchers Program. These educational programs aim to foster development of the next generation of STEM students. Under this project the team of Nirala Singh, Bryan Goldsmith, and Suljo Linic of the University of Michigan is studying electrocatalytic C-N coupling using carbon dioxide and nitrate. Through a joint computational and experimental approach, they will study the reaction mechanism of carbon dioxide and nitrate coupling on metal alloys with a target of increasing selectivity to urea. They will measure the effects of partial pressure of carbon dioxide and concentration of nitrate to identify potential reaction mechanisms and compare with atomistic modeling studies to identify rate-determining and selectivity-determining steps. They will use Raman and X-ray absorption spectroscopies to characterize the electrocatalysts under reaction conditions to better understand the reaction mechanism. They will also investigate the role that linear adsorbate scaling relations have on limiting the urea selectivity, and how the use of novel alloy compositions can avoid these limitations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.