Syouhei Tajima

Niigata University, Niahi-niigata, Niigata, Japan

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Publications (3)6.46 Total impact

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    ABSTRACT: Electrochemical water oxidation by [Ru(EtOtpy)(bpy)OH2]2+ (1) (EtOtpy = 4′-ethoxy-2,2′:6#6°6#′-terpyridine, bpy = 2,2′-bipydidine) was investigated in a homogeneous solution under weakly acidic conditions (pH 5.3). The cyclic voltammogram of a 1 aqueous solution showed that successive proton-coupled electron transfer reactions of RuIIOH2 / RuIIIOH and RuIIIOH/RuIVO redox pairs and high anodic current above 1.1 V vs SCE. Electrocatalytic water oxidation was corroborated by the bulk electrolysis at 1.5 V; the significant amount of O2 was evolved compared with the blank during the electrolysis. Potential-step chronocoulospectrometry (PSCCS) from 0.0 V to 1.52 V vs SCE was conducted to observe the change of 1 in solution during the electrocatalysis. The in situ UV visible spectral change showed oxidation of 1 (RuIIOH2) to RuIIIOH and to further oxidation of RuIIIOH to RuIVO, and that the RuIVO species mainly exists in a steady state after 200 s in the electrocatalysis. The in situ UV–vis spectral change in a reverse potential step from 1.52 V to 0.22 V vs SCE exhibited that RuIIOH2 completely recovers by two electron re-reduction process from the steady state in the electrocatalysis. The observation of RuIVO in a steady state suggests that a rate determining step in the catalytic cycle is oxidation of RuIVO to RuVO rather than the OO bonding formation by nucleophilic attack of water to RuVO in the electrocatalysis in a homogeneous solution.
  • Masayuki Yagi · Syouhei Tajima · Manabu Komi · Hirosato Yamazaki ·
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    ABSTRACT: The catalytic activity of [Ru(tpy)(bpy)OH(2)](2+) (tpy = 2,2':6',2''-terpyridine and bpy = 2,2'-bipyridine) increased by a 4'-substituted ethoxy group on the tpy ligand by more than one order of magnitude to give 1.1 × 10(-1) s(-1) of catalyst turnover frequency, which is comparable with the hitherto-reported champion data.
    Dalton Transactions 04/2011; 40(15):3802-4. DOI:10.1039/c0dt01826k · 4.20 Impact Factor
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    ABSTRACT: Artificial photosynthesis is anticipated as one of the promising clean energy-providing systems for the future. The development of an efficient catalyst for water oxidation to evolve O(2) is a key task to yield a breakthrough for construction of artificial photosynthetic devices. Recently, significant progress has been reported in the development of the molecular catalysts for water oxidation based on manganese, ruthenium and iridium. The molecular aspects of the catalysts reported in the last decade were reviewed to provide hints to design an efficient catalyst, as well as to gain clues to reveal the mechanism of O(2) evolution at photosynthetic oxygen evolving complex in nature.
    Photochemical and Photobiological Sciences 03/2009; 8(2):139-47. DOI:10.1039/b811098k · 2.27 Impact Factor