Now, writing in Joule, Haihui Wang, Jian Xue and colleagues report a proton-conducting membrane reactor for ammonia production that can operate at atmospheric pressure and much lower temperatures than other reactors (300–400 °C) (pictured). The proton-conducting membrane reactor offers an interesting solution to overcome the thermodynamic constraints imposed by the Haber–Bosch process through the design and optimization of the chemical unit with twofold functionality. “This novel electrochemical membrane reactor can integrate the nitrogen reduction reaction (NRR) process and CO2/H2 separation into one unit, providing a feasible direction to promote the development of the ammonia synthesis industry,” explains Wang.
The dense ceramic membrane material, La5.5WO11.25–δ, offers outstanding proton conductivity as well as high CO2 tolerance that gives rise to improved stability. The potential applicability of this process at the industrial scale is corroborated by the high performance of the reactor. A Faradaic efficiency (FE) of 43.8% with a corresponding ammonia production rate of 231.1 µg h–1 cm–2 is achieved at a current density of 2,500 µA cm–2, and the reactor was stable over 100 h of continuous operation. The lower operating temperature represents an important breakthrough in membrane reactor design for sustainable ammonia electrosynthesis. These numbers “outperform most of the state-of-the-art atmospheric NRR reactors,” says Wang.
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