Bioelectrochemical Haber-Bosch process: An ammonia-producing H-2/N-2 fuel cell

Nitrogenases are the only enzymes known to reduce molecular nitrogen (N-2) to ammonia (NH3). By using methyl viologen (N, N\u27-dimethyl-4,4\u27-bipyridinium) to shuttle electrons to nitrogenase, N-2 reduction to NH3 can be mediated at an electrode surface. The coupling of this nitrogenase cathode with a bioanode that utilizes the enzyme hydrogenase to oxidize molecular hydrogen (H-2) results in an enzymatic fuel cell (EFC) that is able to produce NH3 from H-2 and N-2 while simultaneously producing an electrical current. To demonstrate this, a charge of 60 mC was passed across H-2/ N-2 EFCs, which resulted in the formation of 286 nmol NH3 mg (-1) MoFe protein, corresponding to a Faradaic efficiency of 26.4%.This work is supported by a Marie Curie‐Skłodowska Individual Fellowship (Global) under the European Commission\u27s Horizon 2020 Framework (project 654836 “Bioelectroammonia”), the Army Research Office MURI, and Spanish MINECO/FEDER, EU project CTQ2015‐71290‐R. We thank the Seefeldt laboratory for assistance with DT activity assays