Convergence Research Seminar Series: Lea Winter, PhD (Yale University)

Abstract: 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 an unsustainable energy and carbon footprint. Furthermore, inefficiencies in reactive nitrogen management lead to energy losses as well as hazardous environmental pollution. Therefore, electron-driven approaches are needed to establish fossil-free nitrogen interconversions. This talk will focus on electrochemical and plasma-activated nitrogen transformations, which could enable facile coupling to intermittent renewable energy sources to reduce CO2 emissions and reactive nitrogen pollution, facilitate storage and transportation of renewable energy in nitrogen-based fuels, and improve the global distribution of fertilizer to promote food security. 

Non-thermal plasma has been used to synthesize ammonia under mild conditions, but the dearth of fundamental understanding of plasma catalytic reactions handicaps the development of plasma-activated N2 conversion processes. Therefore, an in situ FTIR reactor was employed to elucidate the surface reaction mechanisms and plasma-catalyst interactions. From a practical perspective, technoeconomic and life cycle analysis provide prospects for energy efficiency thresholds and the opportunity to use plasma electrolysis for direct production of fertilizer on agriculturally-relevant scales from air and water. 

Considering the significant losses of reactive nitrogen to the environment, the application of electrified membranes (EMs) as a scalable means of removing or recovering nitrate from wastewater will also be discussed. CNT-based conductive membranes showed significantly higher nitrate reduction efficiency during electrified filtration compared to flow-by mode. The small pore sizes in the membrane reduce the diffusional boundary layer by several orders of magnitude with respect to flow-by mode, overcoming diffusional mass transport limitations and enabling tunable matching of mass transport and reaction timescales. The EMs demonstrated stable nitrate removal to below EPA drinking water limits in synthetic surface water with product selectivity to N2 of over 80%.

Bio: Lea Winter is an Assistant Professor in the Department of Chemical and Environmental Engineering at Yale University. She received her B.S. in Chemical Engineering from Yale in 2015 and Ph.D. in Chemical Engineering from Columbia University as an NSF Graduate Research Fellow in 2020. She received postdoctoral training as a Nanotechnology Enabled Water Treatment (NEWT) Distinguished Postdoctoral Fellow at Yale in 2020–2022. Her research focuses on electrified processes at the food, energy, water, and climate nexus, including development of sustainable and circularized processes for conversion of CO2 to chemicals and fuels, green nitrogen fixation to fertilizers and nitrogen-based fuels, and transformation of contaminants in wastewater into useful products while recovering fit-for-purpose water. Dr. Winter is the recipient of the 2022 Caltech Young Investigator Lecture Series Award, 2019 North American Catalysis Society Kokes Award, and 2018 Columbia Engineering Grossman Scholarship.