Nature uses hydrogenase enzyme to catalyze proton reduction at pH 7 with overpotentials and catalytic efficiencies that rival platinum electrodes. Over the past several years, [FeFe]-hydrogenase ([FeFe]-H₂ase) mimics have been demonstrated to be effective catalysts for light-driven H₂ evolution. However, it remains a significant challenge to realize H₂ production by such an artificial photosynthetic system in neutral aqueous solution. Herein, we report a new system for photocatalytic H₂ evolution working in a broad pH range, especially under neutral conditions. This unique system is consisted of branched polyethylenimine (PEI)-grafted [FeFe]-H₂ase mimic (PEI-g-Fe₂S₂), MPA-CdSe quantum dots (MPA=mercaptopropionic acid), and ascorbic acid (H₂A) in water. Due to the secondary coordination sphere of PEI, which has high buffering capacity and stabilizing ability, the system is able to produce H₂ under visible-light irradiation with turnover number of 10 600 based on the Fe₂S₂ active site in PEI-g-Fe₂S₂. The stability and activity are much better than that of the same system under acidic or basic conditions and they are, to the best of our knowledge, the highest known to date for photocatalytic H₂ evolution from a [FeFe]-H₂ase mimic in neutral aqueous solution.

Chemistry - A European Journal, 2015