Collaborative Research: Electrochemical Production of NH3 Using Proton-Conducting Ceramic Electrolytes

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Ammonia synthesis is essential for production of fertilizers used in food production, along with many other applications. The present method for producing ammonia, the 100-year-old Haber-Bosch process, is based on natural gas and consumes 1-2% of total global energy. It is a high-pressure, high-temperature process that is only economical if used for large-scale production. There would be significant advantages to producing ammonia directly from renewable forms of electricity at the location where it is needed. The goal of this project is to demonstrate that this can be accomplished with high efficiency. This project will seek to develop an electrochemical method for production of ammonia from hydrogen and nitrogen using a proton-conducting, ceramic, solid-oxide electrochemical cell. The central hypothesis is that atmospheric-pressure, ammonia synthesis can be realized by electrochemically driving hydrogen onto catalytic surfaces that are normally limited by high nitride coverage. The project will seek to develop electrode catalysts that are able to dissociate molecular nitrogen, the rate-limiting step in conventional Haber-Bosch synthesis, while simultaneously showing low activity for hydrogen recombination so as to achieve a high hydrogen fugacity at the electrode surface. The project will take advantage of the infiltration methods previously developed for electrode synthesis in Solid Oxide Fuel Cells which allows a wide range of materials to be used for the electrodes. The project will explore mixed electronic-protonic conductors that can be added to the electrode to enhance the three-phase boundary where the electrochemical reaction can occur. The choice of electrocatalysts will be guided by complementary theoretical studies. Small-scale demonstration cells will be produced. If successful, the project will have a dramatic impact on the energy demand and carbon dioxide emissions from ammonia synthesis. The project will support both graduate and undergraduate students in conducting the research, and the PIs will develop faculty-led peer mentorship programs that aim to increase retention of underrepresented undergraduate students in STEM.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.