1996
Challenges and Opportunities Involving Electrochemical Processes for the Sustainable Production of Ammonia

Monday, 14 May 2018: 10:00
Room 614 (Washington State Convention Center)
T. F. Jaramillo (Stanford University)
The massive scale and vital impact of ammonia-based fertilizer production make sustainable and efficient synthesis of ammonia from nitrogen a key goal. Renewably powered, aqueous electrochemical ammonia production represents an enticing strategy to achieve this goal; however, the hydrogen evolution reaction (HER) often dominates under reductive conditions on known electrocatalyst surfaces. Thus, the ability to selectively and catalytically produce ammonia remains a challenge. Our team of experimental and theoretical researchers are pursuing several promising alternative electrochemical approaches to achieve this goal. One strategy is to limit effective proton availability to at the electrocatalyst surface by reducing the bulk proton concentration using dilute H2O in nonaqueous solutions. A range of electrolyte conditions, including varying N2 pressures, pH levels, solvents, and supporting electrolytes have been explored to understand and minimize the loss of Faradaic efficiency to ammonia due to concurrent hydrogen evolution. In a second strategy, we circumvent the HER entirely by implementing an electrochemical stepwise cycling process. The process comprises three distinct steps of surface preparation, nitrogen activation, and ammonia synthesis which can be combined and cycled for continuous ammonia production. Theoretical considerations elucidate the feasibility and general applicability of this cycle as exemplified by a Li-based cycle that demonstrates an initial current efficiency of 89% toward ammonia production.