Low Power Consumption Ammonia Electrosynthesis Using Hydrogen-Nitrate Flow Electrolyzer

Abstract

Ammonia synthesis through electrochemical nitrate reduction has emerged as a promising alternative to the conventional Haber–Bosch process. However, the use of a sluggish oxygen evolution reaction as the anode reaction leads to high energy consumption in nitrate reduction. In this study, we directly utilize hydrogen gas to synthesize ammonia by pairing the hydrogen oxidation reaction with the nitrate reduction reaction. A significantly lower cell voltage for ammonia synthesis was realized on a 16 cm2 flow electrolyzer. We achieved an impressive ammonia yield rate of 16.9 mmol h–1 at a cell voltage of 1.2 V cell voltage. Notably, this approach exhibits a low power consumption of 17 kWh kg–1 of NH3. The mechanism study shows hydroxyl ions generated from water splitting at the cathode cross the anion exchange membrane to react with protons generated from hydrogen oxidation at the anode. Through rigorous technical and economic analyses, this approach is found to be economically viable for industrial synthesis