Photocatalytic Hydrogen Evolution from Rhenium(I) Complexes to [FeFe] Hydrogenase Mimics in Aqueous SDS Micellar Systems: A Biomimetic Pathway

Abstract

To offer an intriguing access to photocatalytic H(2) generation in an aqueous solution, the hydrophobic photosensitizer, Re(I)(4,4'-dimethylbpy)(CO)(3)Br (1) or Re(I)(1,10-phenanthroline)(CO)(3)Br (2), and [FeFe] H(2)ases mimics, [Fe(2)(CO)(6)(mu-adt)CH(2)C(6)H(5)] (3) or [Fe(2)(CO)(6)(mu-adt)C(6)H(5)] (4) [mu-adt = N(CH(2)S)(2)], have been successfully incorporated into an aqueous sodium dodecyl sulfate (SDS) micelle solution, in which ascorbic acid (H(2)A) was used as a sacrificial electron donor and proton source. Studies on the reaction efficiency for H(2) generation reveal that both the close contact and the driving force for electron transfer from the excited Re(I) complexes and [FeFe] H(2)ases mimics are crucial for efficient H(2) generation with visible light irradiation. Steady-state and time-resolved investigations demonstrate that the electron transfer takes place from the excited Re(I) complex 1 or 2 to [FeFe] H(2)ases mimic catalyst 3, leading to the formation of the long-lived Fe(I)Fe(0) charge-separated state that can react with a proton to generate Fe(I)Fe(II).H, an intermediate for H(2) production. As a result, a reaction vessel for the photocatalytic H(2) production in an aqueous solution is established.

Chitosan confinement enhances hydrogen photogeneration from a mimic of the diiron subsite of [FeFe]-hydrogenase

“…As compared with those reported in the literature [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] , the durability and activity of the present system are greatly increased; possibly as a result of the stabilization of the components by chitosan confinement leading to consecutive multi-step electron transfer in equilibrium. The importance of the stabilization was also analysed by exchanging chitosan for relatively small and loose aggregates, anionic SDS (0.166 mol l À 1 ) and cationic CTAB (0.055 mol l À 1 , cetyl trimethyl ammonium bromide) micelles 37 .…”

“…The catalytic performance has been improved from 12.7±1.3 to (5.28 ± 0.17) Â 10 4 turnover numbers under the same condition, which increases 4.16 Â 10 3 folds as compared with the same system without chitosan. These results imply that the environmental protein surrounding catalytic centre might cause the significant activity difference between the diiron subsite of natural 27,37 . The aqueous colloidal MPA-CdTe QDs solution was prepared using the reaction between Cd 2 þ and NaHTe solution according to the literature 45 .…”

“…The importance of the stabilization was also analysed by exchanging chitosan for relatively small and loose aggregates, anionic SDS (0.166 mol l À 1 ) and cationic CTAB (0.055 mol l À 1 , cetyl trimethyl ammonium bromide) micelles 37 . For systematic comparison, the photocatalytic H 2 evolution experiment was carried out from the same reaction system, containing MPA-CdTe QDs, [Fe 2 (CO) 6 (m-adt)CH 2 C 6 H 5 ] catalyst and H 2 A, in SDS and CTAB micelles, respectively.…”

“…From a photochemical point of view, the electron transfer is triggered by the absorption of a photon by a photosensitizer [13][14][15][16][17][18][19][20][21][22][23][24][25] . Since the first attempt by Sun and Åkermark 34 to construct an artificial photocatalytic system for H 2 evolution in 2003, a large number of synthetic model complexes have been pursued to mimic the structure and functionality of the diiron subunit of the natural [FeFe]-H 2 ase H-cluster [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] . It is encouraging to see that the catalytic efficiency for H 2 evolution from artificial photocatalytic systems using mimics of the diiron subsite of [FeFe]-H 2 ase as catalysts has been increased from null to more than hundreds or thousands of turnover numbers (TON) under different irradiation conditions.…”

A Binuclear Iron–Thiolate Catalyst for Electrochemical Hydrogen Production in Aqueous Micellar Solution

“…Other strategies to address the water-solubility issue have included preparation of chemically modified electrodes, [37][38][39] incorporation into cyclodextrin, [40,41] and dispersion in aqueous micellar solutions. [42,43] However, the design of a molecular iron-thiolate catalyst that is capable of using water to produce H 2 with good efficiency remains a significant challenge.…”