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Published May 8, 2003 | public
Journal Article

Effects of Bridging Ligands on the Current−Potential Behavior and Interfacial Kinetics of Ruthenium-Sensitized Nanocrystalline TiO_2 Photoelectrodes

Abstract

We have shown that Ru^(II)(bpy)_2(bpy-4-(xylyl)_x-≡-phenyl-COOH)(PF_6)_2 (abbreviated Rux, where x = 0, 1 or 2 xylyl groups; bpy = 2,2'-bipyridine) dyes can act as sensitizers for nanocrystalline TiO_2 in functional photoelectrochemical cells under simulated solar illumination, albeit with low efficiencies. Both the short-circuit photocurrent density and the open-circuit voltage decreased as x was increased. Electron injection (10^6−10^8 s^(-1)) was slightly faster for the x = 0 dye, but both recombination (10^(-15)−10^(-13) cm^3 s^(-1)) and regeneration (10^4−10^6 s^(-1) for 10 mM I^-) were slightly faster for the x = 2 dye. We suggest that the lack of distance dependence is due to the flexible one-carboxyl attachment to the surface resulting in the Ru−TiO_2 electron-tunneling distance being very similar for x = 0, 1, and 2. For all of the Rux sensitizers, a relatively small potential was needed for generation of current in the dark, indicating that the reaction between electrons in TiO_2 and the I_3^-/I^- electrolyte solution is as favorable for the Rux sensitizers as for unmodified TiO_2 electrodes.

Additional Information

© 2003 American Chemical Society. Received 21 August 2002. Published online 11 April 2003. Published in print 1 May 2003. K.K. thanks the Carlsberg Foundation, Denmark, for a postdoctoral fellowship, and R.V. acknowledges the Link Foundation for funding. This work is supported through NREL subcontract (ACQ-1-30619-09) under DOE contract (DE-AC36-99-G010337). Work on the synthesis and characterization of the Rux complexes was supported by the NSF (H.B.G. and J.R.W.) and by the Arnold and Mabel Beckman Foundation.

Additional details

Created:
August 19, 2023
Modified:
October 25, 2023