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Electrochemical and Photosensitized Redox Reactions of a Prussian Blue Film Layered on a WO 3 /[Ru(bpy) 3 ] 2+ /Polymer Hybrid Film
Author(s) -
Sone Koji,
Teraguchi Masahiro,
Kaneko Takashi,
Aoki Toshiki,
Yagi Masayuki
Publication year - 2007
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200700192
Subject(s) - prussian blue , bilayer , materials science , inorganic chemistry , electrochemistry , chemistry , photoelectrochemistry , ruthenium , electrode , membrane , catalysis , organic chemistry , biochemistry
A hybrid film of WO 3 /tris(2,2′‐bipyridine)ruthenium(II) ([Ru(bpy) 3 ] 2+ )/poly(sodium 4‐styrenesulfonate) (PSS) (denoted as a WRP hybrid film) was prepared as a base layer on an indium tin oxide electrode substrate by cathodic electrodeposition from a colloidal ternary solution containing peroxotungstic acid, [Ru(bpy) 3 ] 2+ , and PSS. Prussian blue, Fe III 4 [Fe II (CN) 6 ] 3 (Fe II –Fe III ) was cathodically electrodeposited on the WRP hybrid film from a Berlin brown (Fe III –Fe III ) colloidal solution to give a WRP/Fe II –Fe III bilayer film. Spectrocyclic voltammetry measurement of the WRP/Fe II –Fe III bilayer film reveals that Prussian white (Fe II –Fe II ) is oxidized to Fe II –Fe III by electrogenerated Ru III , and Fe II –Fe III is re‐reduced to Fe II –Fe II by electrogenerated H x WO 3 . Visible‐light irradiation of the WRP hybrid film generates a small photocurrent (≈8 nA cm −2 ) at 0.4 V of an applied potential, whereas irradiation of the WRP/Fe II –Fe II bilayer film (Fe II –Fe III is electrochemically reduced to the Fe II –Fe II state) significantly generates a steady photoanodic current of 2.0–1.1 μA cm −2 under the same conditions, thus demonstrating that the photoanodic current is produced by the layered Fe II –Fe II film. The photoaction spectrum of the bilayer film reveals that the photoanodic current is based on the photoexcitation of [Ru(bpy) 3 ] 2+ . The photogeneration of Fe II –Fe III from Fe II –Fe II is shown by the absorption spectral change of the bilayer film on irradiation. These results corroborate the notion that Fe II –Fe II is oxidized by photogenerated Ru III to generate Fe II –Fe III . However, the rate of photogeneration of Fe II –Fe III is slow, which could be ascribed to the fast back electron transfer (ET) from WO 3 to Ru III , comparable with the forward ET from Fe II –Fe II to Ru III . The fast back ET could be a crucial problem for the [Ru(bpy) 3 ] 2+ ‐sensitized reaction in the hybrid film.