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Insights into Decomposition Pathways and Fate of Ru(bpy)(3)(2+) during Photocatalytic Water Oxidation with S2O82- as Sacrificial Electron Acceptor

조회수 : 204 등록일 : 2017.01.12 00:00

저자 : Yoon, KB (Yoon, Kyung Byung)
출처 : ACS CATALYSIS
출판일 : 2016.12.01
 
Insights into Decomposition Pathways and Fate of Ru(bpy)(3)(2+) during Photocatalytic Water Oxidation with S2O82- as Sacrificial Electron Acceptor
 
 
Akhtar, US (Akhtar, Umme Sarmeen)[ 3 ] ; Tae, EL (Tae, Eunju Lee); Chun, YS (Chun, Yu Sung); Hwang, IC (Hwang, In Chul); Yoon, KB (Yoon, Kyung Byung)[ 1 ]
 
 
[ 1 ] Sogang Univ, Korea Ctr Artificial Photosynth, Ctr Nanomat, Seoul 121742, South Korea
[ 2 ] Sogang Univ, Dept Chem, Seoul 121742, South Korea
[ 3 ] BCSIR, Inst Glass & Ceram Res Div, Dr Qudraat I Khuda Rd, Dhaka, Bangladesh
 
 
 
The most widely accepted system for homogeneous photocatalytic water oxidation process consists of a water oxidation catalyst, Ru-II(bpy)(3)(2+) as a photopump, and S2O82- as the sacrificial electron acceptor. However, this system is far less than ideal because Ru-II(bpy)(3)(2+) undergoes very rapid decomposition and as a result the process stops before all of the S2O82- is consumed. In this regard its decomposition pathways and the fate of Ru-II(bpy)(3)(2+) should be elucidated to design more efficient photocatalytic water oxidation systems. We found that two pathways exist for decomposition of Ru-II(bpy)(3)(2+) in the light-Ru-II(bpy)(3)2+-S2O82- system. The first is the formation of OH center dot radicals at pH >6 through oxidation of OH- by Ru-III(bpy)(3)(3+) in the dark, which attack the bpy ligand of Ru-II(bpy)(3)(2+). This is a minor, dark decomposition pathway. During irradiation not only Ru-II(bpy)(3)(2+) but also Ru-III(bpy)(3)(3+) becomes photoexcited and the photoexcited Ru-III(bpy)(3)(3+) reacts with S2O82- to produce an intermediate which decomposes into catalytically active Ru mu-oxo dimers when the intermediate concentration is low or into catalytically inactive oligomeric Ru mu-oxo species when the intermediate concentration is high. This is the major, light-induced decomposition pathway. When the Ru-II(bpy)(3)(2+) concentration is low, the light-Ru-II(bpy)(3)(2+)-S2O82- system produces O-2 even in the absence of any added catalysts through the O-2 -producing dark pathway. When the Ru-II(bpy)(3)(2+) concentration is high, the system does not produce O-2 because the overall rate for the light-induced decomposition pathway is much faster than that of the O-2-producing dark pathway.
 
 
 
 
 
 
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