Innovative and Efficient Electrochemical Cycling Strategy Offers Sustainability and High Selectivity for Ammonia Synthesis

Ammonia production is a vital process responsible for fertilizing farmland worldwide and feeding the growing population. Electrification of chemical production processes offers amenability to couple with renewable sources of energy, such as solar or wind power. Electrochemical ammonia production in aqueous solutions from N2 is difficult, however, due to the exceptional stability of the N2 triple bond and due to competition with the hydrogen evolution reaction (HER). Researchers at SUNCAT have developed an alternative strategy to selectively reduce N2 to NH3 using electricity and H2O in a stepwise cycle at ambient pressures. The cycle is demonstrated, as detailed in the research article link below, by first forming a reactive Li surface from LiOH salt electrolysis, then forming Li3N from that Li and N2, and finally hydrolyzing the Li3N to form NH3 and reform the LiOH salt, completing the cycle. This stepwise method allows for selective electrochemical ammonia production by removing protons from the electrochemical step, thus circumventing the HER. The new process yields an initial current efficiency of 88.5% for ammonia production, demonstrating its high selectivity, while approaching industrial level electrolysis current densities. Using UV-Vis and FTIR techniques, NH3 detection was designed to both precisely quantify and isotopically demonstrate that the ammonia produced was indeed from an N2 source. Further, calculations show that this cycling strategy may also be generalized beyond Li for NH3 production, and an ideal candidate will require a lower reduction potential with lower barriers to metal nitridation. This strategy stands in contrast to the conventional Haber Bosch process which typically requires higher pressure, high temperature, and unsustainable fossil fuels to form H2 as a hydrogen source for N2 reduction, while releasing hundreds of million metric tons of CO2 globally per year. Without high pressure infrastructure, this new technology may also be amenable to decentralization, which could increase sustainability with opportunities to mitigate both distribution costs and poor nitrogen utilization in addition to reducing CO2 emissions by not requiring fossil fuels. This research opens a path toward new, sustainable electrochemical processes by demonstrating a high selectivity strategy toward NH3 production­.