(697b) Lithium Mediated Electrochemical Synthesis of Ammonia at High Pressures
AIChE Annual Meeting
2023
2023 AIChE Annual Meeting
Catalysis and Reaction Engineering Division
Nitrogen Chemistry I: Nitrogen Electrochemistry
Tuesday, November 7, 2023 - 12:50pm to 1:10pm
NH3 is an important commodity chemical used to produce fertilizers, explosives, pharmaceuticals, textiles, etc. NH3 is produced by a century-old Haber-Bosch process that is responsible for 1-2% of the total greenhouse gas emissions.1 It is desired to decarbonize NH3 synthesis and green NH3 is one of the candidate materials for H2 storage. Li-mediated electrochemical synthesis of NH3 provides a sustainable and environment-friendly way to make green NH3. Great progress has been made in the Li-mediated NH3 synthesis, but the process suffers from low NH3 current densities, higher cell potentials, and poor electrolyte and substrate stability. For commercializing this technology, we need to solve these challenges. In this study, we address these challenges by choosing an efficient catalyst substrate, electrolyte, protonating source, and reactor design. We enhance the ammonia yield and selectivity by performing the reaction at high pressures ranging from 10-100 bar. A custom electrochemical reactor setup is developed by modifying the autoclave to withstand pressures up to 300 bar. High pressures improve the solubility and diffusion of gaseous nitrogen in non-aqueous solvents, therefore enhancing Lithium nitridation. Various substrates for Li deposition have been studied to optimize the system's performance and Copper electrodeposited on nickel foam is identified as the most promising substrate. Various electrolyte compositions are studied with varying base electrolytes such as THF, propylene carbonate, acetonitrile, and Dimethyl sulfoxide (DMSO). LiOCl4 gives the best Lithium deposition rates. Overall, we report an enhanced NH3 current density of ~-100 mA/cm2 with 50 % NH3 Faradaic efficiency which is the highest reported so far in the literature. The system remains stable for the studied time of 8h.
References
- Capdevila-Cortada, M. Electrifying the HaberâBosch. Nat Catal 2, 1055 (2019)