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Model oxygen‐evolving center composed of polymer membrane and dimer ruthenium complex
Author(s) -
Ramaraj Ramasamy,
Kira Akira,
Kaneko Masao
Publication year - 1995
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1995.220060306
Subject(s) - ruthenium , dimer , catalysis , chemistry , aqueous solution , nafion , redox , photochemistry , membrane , molecule , monomer , inorganic chemistry , medicinal chemistry , electrochemistry , polymer , organic chemistry , biochemistry , electrode
The in situ spectrocyclic voltammetric investigations of the dimeric ruthenium complex used for water oxidation, [(bpy) 2 (H 2 O)Ru–O–Ru(H 2 O)(bpy) 2 ] 4+ (H 2 O–Ru III –Ru III –OH 2 ), were carried out in a homogeneous aqueous solution and in a Nafion membrane under different pH conditions. The in situ absorption spectra recorded for the dimer show that the dimer H 2 O–Ru III –Ru III –OH 2 complex underwent reactions initially to give the detectable H 2 O–Ru III –Ru IV –OH and H 2 O–Ru III –Ru IV –OH 2 complexes, and at higher positive potentials, this oxidized dimer underwent further oxidation to produce a presumably higher oxidation state Ru V –Ru V complex. Since this Ru V –Ru V complex is reduced rapidly by water molecules to H 2 O–Ru III –Ru IV –OH 2 , it could not be detected by absorption spectrum. Independent of the pH conditions and homogeneous solution/Nafion membrane systems, the dimer Ru III –Ru IV was detected at higher potentials, suggesting that the dimer complex acts as a three‐electron oxidation catalyst. However, in the Nafion membrane system it was suggested that the dimer complex may act as a four‐electron oxidation catalyst. While the dimer complex was stable under oxidation conditions, the reduction of the dimer Ru III –Ru III to Ru II –Ru II led to decomposition, yielding the monomeric cis‐[Ru(bpy) 2 (H 2 O) 2 ] 2+ .