Production of H₂O₂ from H₂ and O₂

Hydrogenase enzymes catalyse production and utilization of hydrogen gas, which is considered as a future energy carrier. Scientists at the Max Planck Institute for Terrestrial Microbiology in Marburg and collaborators in the other institute discovered that [Fe]-hydrogenase produces H₂O₂ from H₂ and O₂. This finding is crucial to understand the catalytic mechanism of this enzyme and is also important to design new H₂O₂-forming catalysts.

[Fe]-hydrogenase mediates reversible hydride transfer from H₂ to an organic compound. This catalytic capability makes [Fe]-hydrogenase an attractive model system for designing mimetic hydrogenation catalysts; numerous mimetic compounds of the [Fe]-hydrogenase active site have already been synthesized. To design superior mimetic compounds, a more profound understanding of the reaction of [Fe]-hydrogenase on an atomic basis is necessary.

For industrial use of hydrogenases and their mimic catalysts, sensitivity against O₂ is an important problem because most of the hydrogenases lose activity in the presence of O₂. The research group of Seigo Shima at the Max Planck Institute for Terrestrial Microbiology in Marburg together with Ulrich Ermler from Max Planck Institute of Biophysics, Eckhard Bill from Max Planck Institute for Chemical Energy Conversion, and Kenichi Ataka from Freie Universität Berlin discovered that [Fe]-hydrogenase is only inactivated by O₂ in the presence of reducing substrates. The O₂ added was converted in H₂O₂, which aggressively inactivates the enzyme. This finding indicated that during the catalytic reaction, O₂ is reduced by an intermediate of the [Fe]-hydrogenase to form H₂O₂ (Fig. 1). This is the first experimental evidence of the presence of an O₂-reactive iron-hydride intermediate in the catalytic cycle of [Fe]-hydrogenase, which is of prime importance to understand the reaction mechanism in detail. In addition, this finding paves a new way for developing a biomimetic H₂O₂-producing catalyst, an important industrial compound. H₂O₂ is produced commercially by an indirect chemical process using Ni or Pd as catalyst; however, cleaner and direct processes are preferred. [Fe]-hydrogenase mechanistically catalyses only two-electron reduction with a hydride transfer; therefore, this catalytic reaction should selectively produce H₂O₂. This chemical properties could be applied to design a new H₂O₂-forming catalyst.

Publication:

Huang, G., Wagner, T., Ermler, U. Bill, E., Ataka, K. & Shima, S. (2018)
Dioxygen sensitivity of [Fe]-hydrogenase in the presence of reducing substrates. Angewandte Chemie International Edition. DOI: 10.1002/anie.201712293 and 10.1002/ange.201712293.