Photocatalytic Hydrogen Production Using Models of the Iron–Iron Hydrogenase Active Site Dispersed in Micellar Solution

Abstract

International audienceIron–thiolate complexes of the type [Fe2(μ-bdt)(CO)6−xP(OMe3)x] (bdt=S2C6H4=benzenedithiolate, x≤2) are simplified models of iron–iron hydrogenase enzymes. Recently, we have shown that these water-insoluble organometallic complexes, when included into micelles formed by sodium dodecyl sulfate (SDS), are good catalysts for the electrochemical production of hydrogen in aqueous solutions at pH<6. We herein report that the all-CO derivative [Fe2(μ-bdt)(CO)6] (1), owing to its comparatively low reduction potential, is also a robust molecular catalyst for visible-light-driven production of H2 in aqueous SDS solutions at pH 10.5. Irradiation at λ=455 nm of a system consisting of complex 1, Eosin Y as a sensitizer, and triethylamine as an electron donor produced up to 0.86 mL of H2 in 4.5 h, corresponding to a turnover number of 117 mol of H2 per mol of catalyst. In the presence of a large excess of sensitizer, the production of H2 lasted for more than 30 h, stressing the relative stability of complex 1 under the photocatalytic conditions used herein. Thermodynamic considerations and UV/Vis spectroscopy experiments suggest that the catalytic cycle begins with the photo-driven reduction of complex 1. The reduced intermediate reacts with a proton source to yield iron hydride. Subsequent reduction and protonation steps produce H2, regenerating the starting complex. As a result, the iron–thiolate complex 1 is a versatile proton reduction catalyst that can utilize either solar or electrical energy inputs, providing a starting point for the construction of noble metal-free molecular systems for renewable H2 production

Redox‐Active M8L6 Cubic Hosts with Tetraphenylethylene Faces Encapsulate Organic Dyes for Light‐Driven H2 Production

“…[29] A higher efficiency of hydrogen production was achieveda t pH 11.0. This value is larger than the systems containing an iron-iron hydrogenaser edox catalyst with Fl as photosensitizer, [30] confirming the advantage of the supramolecular system for photocatalytic hydrogen production.C ontrol experiments revealed that the absence of any of these individual components resulted in no hydrogen production andt hat the artificial system did not functionw ell in the absence of light.T he reactions using the mononuclear tris(bipyridine)iron complex, which resembles the corner of the molecular cube as redox catalyst, produces only very small amounts (< 20 mLh ydrogen) under the same experimental conditions with same iron ion concentration. About 0.20 mL hydrogen productionw as achieved at ap Ho f1 1.0.…”

Photo-induced redox catalysis for proton reduction to hydrogen with homogeneous molecular systems using rhodium-based catalysts

“…Some of these homogeneous photocatalytic systems can operate very efficiently (in terms of number of catalytic cycles or turnover number (TON)) in organic or mixed aqueous-organic solvents. Those reaching a turnover number versus catalyst (TON Cat ) above 100 in fully aqueous solution were rare and limited to rhodium [36][37][38][39] and platinum [40] but, since two years, several examples with cobalt [41][42][43][44][45][46][47][48][49][50][51][52][53][54], iron [55][56][57][58] nickel [59] were reported. Developing H 2 -evolving photocatalytic systems functioning in pure water is essential for their coupling with water oxidation systems in photoelectrochemical water-splitting devices.…”

A computational mechanistic investigation of hydrogen production in water using the [RhIII(dmbpy)2Cl2]+/[RuII(bpy)3]2+/ascorbic acid photocatalytic system

“…1 In this context, efficient photocatalytic production of dihydrogen (H 2 ) under visible-light irradiation, which is believed to be a convenient clean energy carrier for the future, is an important goal. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Those operating efficiently in fully aqueous solution were rare and limited to noble-metal based catalysts (rhodium and platinum) [22][23][24][25][26][27] until 2012, when several examples with cobalt, [28][29][30][31][32][33][34][35][36][37][38][39][40][41] iron [42][43][44][45] and nickel-based 46 catalysts were reported. Numerous photocatalytic systems in literature exhibit high activity in organic media or in mixtures of aqueous/organic solvents.…”