Comparison of H2 photogeneration by [FeFe]-hydrogenase mimics with CdSe QDs and Ru(bpy)3Cl2 in aqueous solution. Issue 6 (27th April 2016) - Jian, Jing-Xin
Abstract : Two simple water soluble [FeFe]-H2 ase mimic systems (I and II) were designed to understand the basic principles governing photocatalytic H2 evolution. Abstract : Two water soluble [FeFe]-hydrogenase ([FeFe]-H2 ase) mimics, Fe2 S2 -2SO3 Na (1 ) and Fe2 S2 -SO3 Na (2 ), were designed to compare the performance of photocatalytic H2 evolution systems using quantum dots (QDs) and the molecular photosensitizer [Ru(bpy)3 ] 2+ in water. Under the same conditions, the resulting systems showed that CdSe QDs display much higher activity than [Ru(bpy)3 ] 2+, meanwhile, the turnover numbers (TONs) of 2.65 × 10 4 (1 ) and 1.88 × 10 4 (2 ) for CdSe QD systems and 178 (1 ) and 114 (2 ) for [Ru(bpy)3 ] 2+ systems were comparable with the highest reported H2 evolution systems using the same photosensitizers. Spectroscopic and electrochemical analyses revealed that the excited [Ru(bpy)3 ] 2+ undergoes reductive-quenching while the excited CdSe QDs proceed via oxidative-quenching during the catalytic process. The greater free energy change and faster electron transfer rate in the CdSe QD system made the electron transfer between the photosensitizer and [FeFe]-H2 ase mimics more efficient, which was subsequently corroborated by emission quenching and transient absorption experiments. The reduced [FeFe]-H2 ase mimics generated from the CdSe QDs were demonstrated to react with protons at a rate of 1.17 × 10 7 M −1 s −1 for1 and 8.62 × 10 6 M −1 s −1 for2 .