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Interfacial Electron Transfer Dynamics Following Laser Flash Photolysis of [Ru(bpy) 2 ((4,4′‐PO 3 H 2 ) 2 bpy)] 2+ in TiO 2 Nanoparticle Films in Aqueous Environments
Author(s) -
Brennaman M. Kyle,
Patrocinio Antonio Otávio T.,
Song Wenjing,
Jurss Jonah W.,
Concepcion Javier J.,
Hoertz Paul G.,
Traub Matthew C.,
Murakami Iha Neyde Y.,
Meyer Thomas J.
Publication year - 2011
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201000356
Subject(s) - flash photolysis , chemistry , electron transfer , microsecond , photodissociation , analytical chemistry (journal) , nanosecond , ruthenium , photochemistry , catalysis , laser , reaction rate constant , kinetics , optics , chromatography , quantum mechanics , biochemistry , physics
Nanosecond laser flash photolysis has been used to investigate injection and back electron transfer from the complex [(Ru(bpy) 2 (4,4′‐(PO 3 H 2 ) 2 bpy)] 2+ surface‐bound to TiO 2 ( TiO 2 ‐Ru II ). The measurements were conducted under conditions appropriate for water oxidation catalysis by known single‐site water oxidation catalysts. Systematic variations in average lifetimes for back electron transfer, < τ bet >, were observed with changes in pH, surface coverage, incident excitation intensity, and applied bias. The results were qualitatively consistent with a model involving rate‐limiting thermal activation of injected electrons from trap sites to the conduction band or shallow trap sites followed by site‐to‐site hopping and interfacial electron transfer, TiO 2 (e − )‐Ru 3+ →TiO 2 ‐Ru 2+ . The appearance of pH‐dependent decreases in the efficiency of formation of TiO 2 ‐Ru 3+ and in incident‐photon‐to‐current efficiencies with the added reductive scavenger hydroquinone point to pH‐dependent back electron transfer processes on both the sub‐nanosecond and millisecond–microsecond time scales, which could be significant in limiting long‐term storage of multiple redox equivalents.

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