Artificial water-soluble systems inspired by [FeFe]-hydrogenases for electro- and photocatalytic hydrogen production

[FeFe]-hydrogenases efficiently catalyze the hydrogen evolution reactions (HERs) at rates of up to 10(4) s(-1) with low overpotentials in aqueous media. Although the small-molecule diiron mimetics of the active site of [FeFe]-hydrogenases have been studied for years, most of the synthetic models mediate the catalysis in organic solvents, seriously limiting the application of bioinspired catalytic systems in large-scale H-2 production. Herein, we systematically present the state-of-the-art artificial water-soluble systems inspired by [FeFe]-hydrogenases for potentially electro- and photocatalytic HERs utilizing either electrical or solar energy inputs. The engineering motifs and catalytic properties of these water-soluble mimetic systems have been surveyed and discussed. We hope the present review will shed light on some helpful aspects for designing artificial assembling catalysts for HERs in aqueous milieu and provide mechanistic insights into a broad array of natural oxidoreductases. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.