Continuous ammonia electrosynthesis using physically interlocked bipolar membrane at 1000 mA cm^-2.

Abstract

Electrosynthesis of ammonia from nitrate reduction receives extensive attention recently for its relatively mild conditions and clean energy requirements, while most existed electrochemical strategies can only deliver a low yield rate and short duration for the lack of stable ion exchange membranes at high current density. Here, a bipolar membrane nitrate reduction process is proposed to achieve ionic balance, and increasing water dissociation sites is delivered by constructing a three-dimensional physically interlocked interface for the bipolar membrane. This design simultaneously boosts ionic transfer and interfacial stability compared to traditional ones, successfully reducing transmembrane voltage to 1.13 V at up to current density of 1000 mA cm^-2. By combining a Co three-dimensional nanoarray cathode designed for large current and low concentration utilizations, a continuous and high yield bipolar membrane reactor for NH₃ electrosynthesis realized a stable electrolysis at 1000 mA cm^-2 for over 100 h, Faradaic efficiency of 86.2% and maximum yield rate of 68.4 mg h^-1 cm^-2 with merely 2000 ppm NO₃^- alkaline electrolyte. These results show promising potential for artificial nitrogen cycling in the near future.