Sustainable ammonia production enabled by membrane reactor

The ammonia industry is crucial for the global supply of food through economical production of fertilizers in quantity, and it allows for the development of catalytic chemistry and technologies with ammonia as a promising carbon-free energy carrier. Although the Haber–Bosch process, where hydrogenolysis of nitrogen takes place over a promoted iron catalyst under harsh conditions, will continue to play a key role, its massive carbon footprint and energy consumption call for more sustainable production methods ideally at near ambient pressure. Here, we show a green route for the synthesis of ammonia using a nitrogen permeable membrane reactor. In the absence of an external pressure, our membrane reactor delivers a nitrogen flux of 3.1 × 10−2 ml cm−2 h−1, leading to an ammonia yield rate of 2.9 μmol cm−2 h−1 at 450 °C. The reaction of permeated N3− ions with H2 gives rise to a high ammonia concentration of 0.097 vol% in the gas phase, which is close to the limit of thermodynamic equilibrium (0.1 vol%) under the identical condition. This work not only creates a greener path for ambient-pressure ammonia synthesis but also presents a new membrane reactor design that could find applications in other areas.