Bioelectrochemical Haber-Bosch Process: An Ammonia-Producing H /N Fuel Cell.

Nitrogenases are the only enzymes known to reduce molecular nitrogen (N ) to ammonia (NH ). By using methyl viologen (N,N'-dimethyl-4,4'-bipyridinium) to shuttle electrons to nitrogenase, N reduction to NH 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 ) results in an enzymatic fuel cell (EFC) that is able to produce NH from H and N while simultaneously producing an electrical current. To demonstrate this, a charge of 60 mC was passed across H  /N EFCs, which resulted in the formation of 286 nmol NH  mg MoFe protein, corresponding to a Faradaic efficiency of 26.4 %.