Professor Shelley D. Minteer

The Haber-Bosch process, responsible for producing NH3 from H2 and N2, ranks as one of the most important discoveries in the history of chemistry. Its industrial application in synthetic fertilizers contributed to the continuously increasing population and their quality of life. The Haber-Bosch process, however, is a very energy-intensive process with high temperature (500 °C) and pressure (20 MPa) required for efficient NH3 production. Over 1 % of the world's energy sources were consumed in order to produce ~140 megatons of NH3 in 2015. Additionally, 3 % of global CO2 emissions are due to the Haber-Bosch related technology. A renewable strategy for ammonia production would therefore be valuable. In nature, the ability to reduce N2 to NH3 is limited to a group of bacteria and archaea classified as diazotrophs, all of which share an enzyme called nitrogenase. Using methylviologen (N,N'-dimethyl-4,4'-bipyridinium) to shuttle electrons to nitrogenase, N2 reduction to NH3 can be mediated at an electrode surface. The coupling of this nitrogenase cathode with a bioanode which utilizes the enzyme hydrogenase to oxidize molecular hydrogen (H2) results in an enzymatic fuel cell (EFC) that is able to produce NH3 from H2 and N2, while simultaneously producing an electrical current. To demonstrate this, 60 mC of charge was passed across H2/N2 EFCs, which resulted in the formation of 286 nmol NH3 mg-1 MoFe protein, corresponding to a Faradaic efficiency of 26.4 %. Importantly, this EFC produces NH3 and electrical energy in a carbon-neutral manner. A protective Fell protein, which can reversibly lock nitrogenase into a multicomponent protective complex upon exposure to low concentrations of 02, was incorporated into a nitrogenase bioelectrosynthetic cell whereby NH3 was produced using air as a substrate. This marks a significant step forward in overcoming the crippling limitation of nitrogenase's sensitivity toward O2. Finally, this talk will discuss Bioelectrochemical strategies for eliminating the ATP-dependence of this reaction.

Shelley D. Minteer

Prof. Shelley Minteer is the Dale and Susan Poulter Endowed Chair of Biological Chemistry and Associate Chair of Chemistry at the University of Utah. Prof. Minteer is also the director of the NSF Center for Synthetic Organic Electrochemistry. Prof. Minteer’s research focuses on improving the abiotic-biotic interface between biocatalysts and electrode surfaces for enhanced bioelectrocatalysis. These biocatalysts include microbial cells, organelles, redox proteins, and oxidoreductase enzymes. The Minteer group utilizes a variety of electroanalytical techniques (linear polarization, cyclic voltammetry, differential pulse voltammetry, differential pulse amperometry), as well as a variety of biological and spectroscopic techniques to accomplish these goals.