Browsing by Author "Chen, Mei-Hua"

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A Ruthenium-Based Biomimetic Hydrogen Cluster for Efficient Photocatalytic Hydrogen Generation from Formic Acid
(2015-04-20)
Chang, Chin-Hao
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Chen, Mei-Hua
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Du, Wan-Shan
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Gliniak, Jacek
;
Lin, Jia-Hoa
A ruthenium-based biomimetic hydrogen cluster, [Ru-2(CO)(6)(-SCH2CH2CH2S)] (1), has been synthesized and, in the presence of the P ligand tri(o-tolyl)phosphine, demonstrated efficient photocatalytic hydrogen generation from formic acid decomposition. Turnover frequencies (TOFs) of 5500h(-1) and turnover numbers (TONs) over 24700 were obtained with less than 50ppm of the catalyst, thus representing the highest TOFs for ruthenium complexes as well as the best efficiency for photocatalytic hydrogen production from formic acid. Moreover, 1 showed high stability with no significant degradation of the photocatalyst observed after prolonged photoirradiation at 90 degrees C.
Enhanced hydrogen generation from formic acid by a biomimetic ruthenium complex with a covalently bonded phosphine ligand
(2017-04-13)
Chen, Mei-Hua
;
Lin, Jia-Hoa
;
Li, Chuen-Ru
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Gliniak, Jacek
;
Chang, Chin-Hao
A series of [Ru-2(CO)(5)(mu-SCH2CH2CH2S)PXS] complexes (Ru-2-S-2-PXS, X = phosphine ligands, S = 1-8) have been synthesized and evaluated for their photocatalytic H-2 generation efficiencies from formic acid decomposition. The [Ru-2(CO)(5)(mu-SCH2CH2CH2S)P(o-C6H4CH3)(3)] (Ru-2-S-2-PX4) catalyst + P(CH3)(3) ligand exhibited a high turnover frequency of 15,840h(-1) and turnover number of 24,536. A mechanistic investigation of the Ru-2-S-2-PX4 + FA/TEA catalyzed photocatalytic H-2 generation reaction using ATR-IR, EI-MS, and NMR techniques suggested that when Ru2-S2-PX4 was photoirradiated, the P(o-C6H4CH3)(3) was dissociated from the complex to form a new species, [Ru-2(CO)(5)(mu-SCH2CH2CH2S)]* (I). The free P(o-C6H4CH3)(3) then attacks a second molecule of Ru-2-S-2-PX4 to form Ru-2-S-2-(PX4)(2) and release of free CO, which is then combined with species I to form Ru-2-S-2. Subsequent attachment of formate ion to species Ru-2-S-2-PX4, Ru-2-S-2, and Ru-2-S-2-(PX4)(2) to form [Ru-2(CO)(5)(mu-SCH(2)CH(2)CH(2)SA]-HC00(-) (II), Ru-2-S-2-HCOO- (II') and Ru-2-S-2-PX4-HCOO- (II"), respectively. Rearrangement of complex II (or II' or II") and evolution of CO2 generate a transient complex [Ru-2(CO)(5)(mu-SCH2CH2CH2S)H (III), which then undergoes a protonation process to yield complex [Ru-2(CO)(5)(mu-SCH2CH2CH2S)H-2] (IV). Release of H-2 and re-incorporation of the formate anion as well as evolution of CO2 regenerates the active complex III and the cycle begins again. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.