title: Electrochemical Instability of Phosphonate-Derivatized, Ruthenium(III) Polypyridyl Complexes on Metal Oxide Surfaces.
abstract: The oxidative stability of the molecular components of dye-sensitized photoelectrosynthesis cells for solar water splitting remains to be explored systematically. We report here the results of an electrochemical study on the oxidative stability of ruthenium(II) polypyridyl complexes surface-bound to fluorine-doped tin oxide electrodes in acidic solutions and, to a lesser extent, as a function of pH and solvent with electrochemical monitoring. Desorption occurs for the Ru(II) forms of the surface-bound complexes with oxidation to Ru(III) enhancing both desorption and decomposition. Based on the results of long-term potential hold experiments with cyclic voltammetry monitoring, electrochemical oxidation to Ru(III) results in slow decomposition of the complex by 2,2'-bipyridine ligand loss and aquation and/or anation. A similar pattern of ligand loss was also observed for a known chromophore-catalyst assembly for both electrochemical water oxidation and photoelectrochemical water splitting. Our results are significant in identifying the importance of enhancing chromophore stability, or at least transient stability, in oxidized forms in order to achieve stable performance in aqueous environments in photoelectrochemical devices.
authors: †Department of Chemistry, Virginia Military Institute, Lexington, Virginia 24450, United States.
authors: Jacob T
authors: JT
authors: Hyde
authors: ‡Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
authors: Kenneth
authors: K
authors: Hanson
authors: ‡Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
authors: Aaron K
authors: AK
authors: Vannucci
authors: ‡Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
authors: Alexander M
authors: AM
authors: Lapides
authors: ‡Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
authors: Leila
authors: L
authors: Alibabaei
authors: ‡Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
authors: Michael R
authors: MR
authors: Norris
authors: ‡Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
authors: Thomas J
authors: TJ
authors: Meyer
authors: †Department of Chemistry, Virginia Military Institute, Lexington, Virginia 24450, United States.
authors: Daniel P
authors: DP
authors: Harrison
keywords: chromophore; dye-sensitized; electrochemistry; interfaces; phosphonate; photoelectrosynthesis; ruthenium; stability