title: Branched polyethylenimine improves hydrogen photoproduction from a CdSe quantum dot/[FeFe]-hydrogenase mimic system in neutral aqueous solutions.
abstract: Nature uses hydrogenase enzyme to catalyze proton reduction at pH 7 with overpotentials and catalytic efficiencies that rival platinum electrodes. Over the past several years, [FeFe]-hydrogenase ([FeFe]-H2 ase) mimics have been demonstrated to be effective catalysts for light-driven H2 evolution. However, it remains a significant challenge to realize H2 production by such an artificial photosynthetic system in neutral aqueous solution. Herein, we report a new system for photocatalytic H2 evolution working in a broad pH range, especially under neutral conditions. This unique system is consisted of branched polyethylenimine (PEI)-grafted [FeFe]-H2 ase mimic (PEI-g-Fe2 S2 ), MPA-CdSe quantum dots (MPA=mercaptopropionic acid), and ascorbic acid (H2 A) in water. Due to the secondary coordination sphere of PEI, which has high buffering capacity and stabilizing ability, the system is able to produce H2 under visible-light irradiation with turnover number of 10 600 based on the Fe2 S2 active site in PEI-g-Fe2 S2 . The stability and activity are much better than that of the same system under acidic or basic conditions and they are, to the best of our knowledge, the highest known to date for photocatalytic H2 evolution from a [FeFe]-H2 ase mimic in neutral aqueous solution.
authors.affiliation: Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry & University of Chinese Academy of Sciences, Beijing 100190 (P.R. China), Fax: (+86) 10-8254-3580.
authors.forename: Wen-Jing
authors.initials: WJ
authors.lastname: Liang
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Min
authors.initials: M
authors.lastname: Wen
authors.forename: Jing-Xin
authors.initials: JX
authors.lastname: Jian
authors.forename: Xu-Zhe
authors.initials: XZ
authors.lastname: Wang
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.forename: Chen-Ho
authors.initials: CH
authors.lastname: Tung
authors.forename: Li-Zhu
authors.initials: LZ
authors.lastname: Wu
mesh_terms: D032701:Biomimetics; D006859:Hydrogen / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D055668:Photochemical Processes; D011094:Polyethyleneimine / Q000737:chemistry*; D045663:Quantum Dots; D014867:Water
chemical_list: D007506:Iron-Sulfur Proteins; D014867:Water; D006859:Hydrogen; D011094:Polyethyleneimine; D006864:Hydrogenase
keywords: [FeFe]-hydrogenase; artificial photosynthesis; electron transfer; hydrogen; photochemistry; polyethylenimine