Ammonia was successfully synthesized by using a new electrochemical reaction with high current efficiency at atmospheric pressure and at lower temperatures than the Haber-Bosch process. In this method, nitride ion (N3-), which is produced by the reduction from nitrogen gas at the cathode, is anodically oxidized and reacts with hydrogen to produce ammonia at the anode.

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The kinetics of a novel ammonia synthesis reaction ͑N 3− + 3/2H 2 → NH 3 + 3e − ͒ in molten salts were investigated. To evaluate current efficiencies and ammonia synthesis rates, potentiostatic electrolyses were conducted under various electrolysis conditions in molten LiCl-KCl-CsCl containing 0.5 mol % Li 3 N. The ammonia synthesis rate depended on the hydrogen partial pressure of the feed gas, not on the electrolysis potential. The relationship between ammonia synthesis rate and temperature was described by the Arrhenius equation, and the activation energy of the ammonia synthesis reaction was 69 kJ mol −1 . From the obtained results, the mechanism of the ammonia synthesis reaction was discussed.

The dissolution behavior of ammonia (NH 3 ) in a molten LiCl-KCl-CsCl system was studied in order to determine the feasibility of low-energy NH 3 production via electrochemical synthesis in a high temperature molten salt system. In the presence of nitride ion (N 3− ), a portion of NH 3 chemically dissolved in the melt as imide (NH 2− ) and amide (NH 2 − ) anions formed by the reaction between N 3− and NH 3 . Although the dissolved NH 2 − anion thermally decomposed to form NH 3 and NH 2− anion, this phenomena may lower the yield of electrochemical NH 3 production. The dissolved NH 3 can be recovered by supplying hydrogen or water vapor to the melt. The anodic reaction between N 3− and H 2 to form NH 3 at a hydrogen gas-diffusion electrode was also examined and the NH 3 yield was estimated. Although the competing N 2 evolution reaction occurred at potentials more positive than 1.2 V vs. Li(I)/Li, the conversion of Li 3 N approached 70%, following the recovery processes.