(446g) Continuous Lithium-Mediated Ammonia Synthesis at Ambient Conditions

Ammonia produced by the Haber Bosch process is essential as a source of nitrogen in a wide range of downstream fertilizers, plastics, and commodity chemicals. While this route has improved significantly over the past century, it still leads to the production of a stoichiometric carbon dioxide footprint due to the use of methane as a hydrogen source, and elevated temperature and pressure limit the modularity. Our lab is developing a continuous lithium-mediated approach in which nitrogen is fixed at ambient conditions. Through interrogating the order-dependence of the reaction, we have uncovered a reaction network through which lithium mediates the fixation of nitrogen versus competing hydrogen evolution. We have also uncovered how transport plays a large role in this reaction, as we have approached rates that are close to the transport-limited current density. A coupled-transport kinetic model has provided insights for optimizing the reactor for higher rates or higher selecitivities of ammonia synthesis. We will provide a roadmap by which this process can continue to be improved through further studies.