Photochemical,Electrochemical, and Photoelectrochemical Water Oxidation Catalyzed by Water‐Soluble Mononuclear Ruthenium Complexes |
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| Authors: | Ting‐Ting Li Wei‐Liang Zhao Prof?Dr Yong Chen Fu‐Min Li Chuan‐Jun Wang Yong‐Hua Tian Prof?Dr Wen‐Fu Fu |
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| Institution: | 1. Key Laboratory of Photochemical Conversion and Optoelectronic, Materials and HKU‐CAS Joint Laboratory on New Materials, Technical Institute of Physics and Chemistry, University of Chinese Academy of Sciences, CAS, Beijing 100190 (P. R. China), Fax: (+86)?10‐6255‐4670;2. College of Chemistry and Engineering, Yunnan Normal University, Kunming 650092 (P. R. China) |
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| Abstract: | Two mononuclear ruthenium complexes Ru(H2tcbp)(isoq)2] ( 1 ) and Ru(H2tcbp)(pic)2] ( 2 ) (H4tcbp=4,4′,6,6′‐tetracarboxy‐2,2′‐bipyridine, isoq=isoquinoline, pic=4‐picoline) are synthesized and fully characterized. Two spare carboxyl groups on the 4,4′‐positions are introduced to enhance the solubility of 1 and 2 in water and to simultaneously allow them to tether to the electrode surface by an ester linkage. The photochemical, electrochemical, and photoelectrochemical water oxidation performance of 1 in neutral aqueous solution is investigated. Under electrochemical conditions, water oxidation is conducted on the deposited indium‐tin‐oxide anode, and a turnover number higher than 15,000 per water oxidation catalyst (WOC) 1 is obtained during 10 h of electrolysis under 1.42 V vs. NHE, corresponding to a turnover frequency of 0.41 s?1. The low overpotential (0.17 V) of electrochemical water oxidation for 1 in the homogeneous solution enables water oxidation under visible light by using Ru(bpy)3]2+ ( P1 ) (bpy=2,2′‐bipyridine) or Ru(bpy)2(4,4′‐(COOEt)2‐bpy)]2+ ( P2 ) as a photosensitizer. In a three‐component system containing 1 or 2 as a light‐driven WOC, P1 or P2 as a photosensitizer, and Na2S2O8 or CoCl(NH3)5]Cl2 as a sacrificial electron acceptor, a high turnover frequency of 0.81 s?1 and a turnover number of up to 600 for 1 under different catalytic conditions are achieved. In a photoelectrochemical system, the WOC 1 and photosensitizer are immobilized together on the photoanode. The electrons efficiently transfer from the WOC to the photogenerated oxidizing photosensitizer, and a high photocurrent density of 85 μA cm?2 is obtained by applying 0.3 V bias vs. NHE. |
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| Keywords: | electrochemistry photochemistry photoelectrochemistry ruthenium complex water oxidation |
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