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Photoelectrochemistry of Tris(bipyridyl)ruthenium(II) covalently attached to n-type SnO/sub 2/

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00537a021· OSTI ID:6861614

Ru(bpy)/sub 3//sup 2 +/ (bpy = 2,2'-bipyridyl) has been covalently attached to n-type SnO/sub 2/ via condensation of surface hydroxyl groups with ruthenium 4-(trichlorosilylethyl)-4'-methyl-2,2'-bipyridine)bis(2,2'-bipyridine) bis(hexafluorophosphate)). A thick coating (approx. 1000 layers, based on the surface hydroxyl group concentration) was produced, presumably via oligomerization of hydrolyzed -SiCl/sub 3/ groups. The coating, which was stable to organic solvents as well as to aqueous acids and bases, gave reversible cyclic voltammograms, with peak potentials shifted slightly from those of aqueous Ru(bpy)/sub 3//sup 2 +/, but the number of electroactive molecules corresponded only to a few layers. The coated electrode gave a photocurrent about twice that observed for SnO/sub 2/ in contact with aqueous 4 mM Ru(bpy)/sub 3//sup 2 +/, with a slightly red-shifted excitation spectrum. Only a small fraction of the electroactive molecules appeared to participate in excited-state electron transfer, although a steady-state current was supported, presumably by slow electron transfer from the outer layers. Prolonged illumination produces extensive hydrolysis of the outer layers of the coating, but a modest reduction of electroactivity, and only a slight decrease in photocurrent. The photocurrent increases with applied potential, then reaches a plateau, and falls off again near the reduction potential of Ru(bpy)/sub 3//sup 2 +/*; the falloff is attributed to back-electron transfer via tunneling through the thin space charge layer.

Research Organization:
Princeton Univ., NJ
OSTI ID:
6861614
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 102; ISSN JACSA
Country of Publication:
United States
Language:
English

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