Unraveling Photo-Driven H2 Production with a Bio-Inspired NiFe Complex: Revealing an Unexpected Hydrogen Atom Source

Developing efficient photocatalytic systems for sustainable H₂ production is a crucial step toward reducing dependence on fossil fuels. While extensive research over the past two decades has focused on bioinspired FeFe catalysts, NiFe-based systems remain largely unexplored. This study addresses that gap by introducing the first heterodinuclear NiFe complex capable of catalyzing H₂ production under photoassisted conditions. The catalyst demonstrates remarkable performance, achieving a turnover frequency of 2750 h^-1 and a turnover number of up to 41200. A comprehensive mechanistic investigation, supported by EPR and labeling experiments, reveals that the photodriven catalytic pathway differs from the electrocatalytic mechanism. Under photoassisted conditions, BIH not only serves as a sacrificial electron donor, but its oxidized form, BIH^·+, also acts as a hydrogen atom donor, directly contributing to the high activity of this system. These findings highlight the dual role of BIH in photoassisted catalysis, extending beyond its specific application in H₂ production to other reactions of interest, such as CO₂ reduction.