Session: 01-02: Decarbonizing Commodity Chemicals and Emissions Analyses

Paper Number: 169841

169841 - Modeling and Flow Cell Measurements for Electrochemical Nitrate-to-Ammonia Conversion 

Abstract: 

Global ammonia (NH3) production is projected to increase by 40% by 2050, driven by population growth and the subsequent rise in fertilizer use. Traditional ammonia production relies on the fossil fuel-intensive Haber-Bosch process, which generates about 500 megatons of carbon dioxide (CO2) annually and accounts for 1.3% of global emissions. Additionally, excessive fertilizer use pollutes ground and surface waters with nitrates (NO3-), nitrites (NO2-), and ammonia. Transitioning to electrochemical processes offers a promising solution by utilizing renewable electricity to convert wastewater nitrates into ammonia. This approach not only reduces anthropogenic emissions associated with fertilizer production but also helps remove nitrogen contaminants from water, fostering the development of a circular economy. Recent advancements have been made in developing selective electrocatalysts; however, the interaction between design and operational parameters—such as fluid flow, mass and charge transport, and kinetics within electrochemical flow cells—remains underexplored. To enhance the selectivity and conversion rates of nitrate to ammonia, a continuum model at the boundary layer scale investigates the effects of operating conditions such as pulsed electrolysis and pulsed flow electrolyte. This study utilizes kinetic parameters obtained from experimental data using three-electrode cells and H-cells for planar and cubed Cu catalysts, respectively, and it aids to understand the interplay of local pH, nitrate concentrations, and buffering species. We study methods to reduce the diffusion boundary layer thickness at the gas diffusion electrode where nitrate reduction occurs, we identify design and operational strategies for passive flow control techniques, such as interior surface ridge flow channels, to guide testing at the flow-cell scale in order to improve current densities. Ultimately, these models and experiments will provide insights into the challenges and opportunities for the co-reduction of NO3- and CO2 in the context of electrochemical urea synthesis

Presenting Author: Fernando Villavicencio University of Michigan - Ann Arbor

Presenting Author Biography: Fernando A. Villavicencio earned his Bachelor of Science degree in Mechanical Engineering from the University of Wisconsin, Madison, in 2016. He began his career in the automotive industry in Dearborn, Michigan, participating in a rotational program as a product development engineer from 2016 to 2019. He then advanced to the role of Controls Integration Engineer, contributing to the development of hybrid electric vehicle technology until 2024. After completing his Master’s degree at the University of Michigan in 2024, Fernando continued to pursue a Ph.D. in Mechanical Engineering at the same institution. His research examines the effects of flow cell design and dynamic operation on the electrochemical reduction of nitrate to ammonia and explores its implications for the co-reduction of carbon dioxide and nitrate in urea production.