Performance and Possible Mechanism of Photocatalytic Water Splitting for Hydrogen Production Based on Two [2Fe2S] Compounds

Two new [2Fe2S] compounds 1 and 2 containing the bridging ligand 6, 8-lipoic acid methyl ester (pdte) were synthesized, and their structures were characterized by IR, 1 HNMR, 31 PNMR (compound 2), elemental analysis and X-ray single crystal diffraction (compound 1), etc. A three-component photo-catalytic hydrogen production system was constructed, in which compounds 1 or 2 was used as the photo-catalyst, EY2- as the photo-sensitizer, TEA as the electron donor and proton source, respectively. The results showed that the maximum hydrogen production was 106. 5 μmol (TON 13. 3 vs. 1) and 136. 2 μmol (TON 17 vs. 2), with corresponding hydrogen production rates 7 607 μmol·g-1·h-1 and 6 595. 6 μmol·g-1·h-1, respectively, under the optimal hydrogen production conditions of V(CH3 CN)/ V(H2 O)= 1 / 1, pH = 11, and visible light (λ>420 nm) irradiation for 3. 5 h. Probing into the mechanism of hydrogen production, it was shown that the deactivation of the system was mainly due to the photo-degradation of the photo-sensitizer EY2- and the catalyst in the photo-catalytic process. Photogenerated electrons can be transferred from 1* EY2- or EY3-·to the FeI FeI center via two pathways to form the important intermediate FeI Fe0 species in the present system. Furthermore, the important hydrogen-producing active intermediates HFeII FeI species and (η2 -H2) FeII -FeI species were formed by further protonation, finally releasing H2 and regenerating FeI FeI species. The result implicated that the title catalyst (especially 2) was a potential molecular catalyst for photo-catalytic hydrogen production. © 2023 Cailiao Daobaoshe/ Materials Review. All rights reserved.