The roles of chalcogenides in O 2 protection of H 2 ase active sites.

At some point, all HER (Hydrogen Evolution Reaction) catalysts, important in sustainable H ₂ O splitting technology, will encounter O ₂ and O ₂ -damage. The [NiFeSe]-H ₂ ases and some of the [NiFeS]-H ₂ ases, biocatalysts for reversible H ₂ production from protons and electrons, are exemplars of oxygen tolerant HER catalysts in nature. In the hydrogenase active sites oxygen damage may be extensive (irreversible) as it is for the [FeFe]-H ₂ ase or moderate (reversible) for the [NiFe]-H ₂ ases. The affinity of oxygen for sulfur, in [NiFeS]-H ₂ ase, and selenium, in [NiFeSe]-H ₂ ase, yielding oxygenated chalcogens results in maintenance of the core NiFe unit, and myriad observable but inactive states, which can be reductively repaired. In contrast, the [FeFe]-H ₂ ase active site has less possibilities for chalcogen-oxygen uptake and a greater chance for O ₂ -attack on iron. Exposure to O ₂ typically leads to irreversible damage. Despite the evidence of S/Se-oxygenation in the active sites of hydrogenases, there are limited reported synthetic models. This perspective will give an overview of the studies of O ₂ reactions with the hydrogenases and biomimetics with focus on our recent studies that compare sulfur and selenium containing synthetic analogues of the [NiFe]-H ₂ ase active sites.
Competing Interests: There are no conflicts to declare.
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