Efficient electrochemical conversion of nitric oxide to ammonia using a porous nickel catalyst in a membrane electrode assembly electrolyzer

Abstract

The electrochemical synthesis of ammonia presents a promising pathway to decarbonize and electrify the production of the world’s second-largest commodity chemical. Among potential reactants, NO_x gases stand out owing to their favorable thermodynamics, advantageous kinetics, and availability from both combustion emissions and nitrogen-fixation processes, such as plasma-induced atmospheric nitrogen oxidation. However, the typically low concentration of NO_x in these sources poses significant challenges for electrochemical performance, particularly due to limitations in reactant mass transport. In this work, we report on the use of a porous nickel catalyst in a membrane electrode assembly (MEA) electrolyzer to enable the direct use of a dilute nitric oxide (NO) feed. The rational optimization of reactant mass transport led to the attainment of maximum values of NO-to-NH₃ single-pass conversion of 93%, faradaic efficiency for ammonia of 92%, and ammonium production rate of 556 μmol/h⋅cm².