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Continuous-flow electrosynthesis of ammonia by nitrogen reduction and hydrogen oxidation

2023; American Association for the Advancement of Science; Volume: 379; Issue: 6633 Linguagem: Inglês

10.1126/science.adf4403

1095-9203

Xianbiao Fu, Jakob B. Pedersen, Yuanyuan Zhou, Mattia Saccoccio, Shaofeng Li, Rokas Sažinas, Katja Li, Suzanne Z. Andersen, Aoni Xu, Niklas H. Deissler, Jon Bjarke Valbæk Mygind, Chao Wei, Jakob Kibsgaard, Peter C. K. Vesborg, Jens K. Nørskov, Ib Chorkendorff,

Electrocatalysts for Energy Conversion

Ammonia is a critical component in fertilizers, pharmaceuticals, and fine chemicals and is an ideal, carbon-free fuel. Recently, lithium-mediated nitrogen reduction has proven to be a promising route for electrochemical ammonia synthesis at ambient conditions. In this work, we report a continuous-flow electrolyzer equipped with 25-square centimeter-effective area gas diffusion electrodes wherein nitrogen reduction is coupled with hydrogen oxidation. We show that the classical catalyst platinum is not stable for hydrogen oxidation in the organic electrolyte, but a platinum-gold alloy lowers the anode potential and avoids the decremental decomposition of the organic electrolyte. At optimal operating conditions, we achieve, at 1 bar, a faradaic efficiency for ammonia production of up to 61 ± 1% and an energy efficiency of 13 ± 1% at a current density of -6 milliamperes per square centimeter.