Caltech Young Investigators Lecture
Nitrogen fixation in fertilizers forms the basis of modern agriculture and mediates global food insecurity. However, conventional thermally-activated nitrogen conversion processes consume substantial amounts of fossil fuels as materials and energy inputs, leading to unsustainable energy and carbon footprints. Furthermore, inefficiencies in reactive nitrogen management lead to environmental pollution and imbalances in the biogeochemical nitrogen cycle. Electrified approaches are needed to establish fossil-free, efficient nitrogen interconversions that are compatible with renewable electricity.
Non-thermal plasma has been used to synthesize ammonia under mild conditions, but the dearth of fundamental understanding of plasma-catalytic reactions hampers the development of efficient plasma-catalytic N2 conversion. Therefore, an in situ FTIR reactor was employed to elucidate the surface reaction mechanisms and plasma-catalyst interactions. A techno-economic analysis revealed the threshold efficiency required for a plasma process to become environmentally and economically competitive.
Beyond electrification of N2 fixation to NH3, waste streams containing fixed nitrogen as nitrate may be mined for reactive nitrogen recovery or rebalancing the nitrogen cycle, via nitrate electrochemical reduction. Electrified membranes (EMs) were fabricated and functionalized with non-precious metal electrocatalysts. The EMs showed significantly higher nitrate removal efficiency during electrified filtration compared to diffusion mode. In addition to the environmental impacts of closing the nitrogen loop by converting NO3– into innocuous N2, the prospects for nitrate conversion to NH3 for recovery as fertilizer or nitrogen-based fuels were analyzed for various source waters.
Lea R. Winter is a Nanotechnology Enabled Water Treatment (NEWT) Distinguished Postdoctoral Fellow in Chemical and Environmental Engineering at Yale University. Her work in the research group of Prof. Menachem Elimelech focuses on the development of sustainable reactive electrochemical membranes for water decontamination and conversion of nitrate in wastewaters into valuable products. She will be starting as an Assistant Professor in the same department in Summer 2022. Lea received her Ph.D. in Chemical Engineering at Columbia University with Prof. Jingguang Chen. As an NSF Graduate Research Fellow, she researched the conversion of CO2 and N2 to chemicals and fuels using non-precious metal heterogeneous catalysts and non-thermal plasma activation. Lea obtained her B.S. in Chemical Engineering from Yale University, where she researched water treatment and desalination. She also completed fellowships abroad in combustion of nitrogen-based fuels at the Technion Institute; plasma modification of polymer surfaces at the École Nationale Supérieure de Chimie de Paris; and immunogenomics at the Weizmann Institute. Lea founded SciRISE at Columbia, a high school internship program for students who recently immigrated to the U.S. to pursue independent research projects, and she co-founded the Yale Summer Science Research Institute.
This talk is part of the Caltech Young Investigators Lecture Series, sponsored by the Division of Engineering and Applied Science.