Fundamental Factors Impacting the Stability of Phosphonate-Derivatized Ruthenium Polypyridyl Sensitizers Adsorbed on Metal Oxide Surfaces
- Virginia Military Inst., Lexington, VA (United States). Dept. of Chemistry
- Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry
A series of 18 ruthenium(II) polypyridyl complexes were synthesized and evaluated under electrochemically oxidative conditions, which generates the Ru(III) oxidation state and mimics the harsh conditions experienced during the kinetically limited regime that can occur in dye-sensitized solar cells (DSSCs) and dye-sensitized photo-electrosynthesis cells, to further develop fundamental insights into the factors governing molecular sensitizer surface stability in aqueous 0.1 M HClO4. Both desorption and oxidatively induced ligand substitution were observed on planar fluorine-doped tin oxide (FTO) electrodes, with a dependence on the E1/2 Ru(III/II) redox potential dictating the comparative ratios of the processes. Complexes such as RuP4OMe (E1/2 = 0.91 vs Ag/AgCl) displayed virtually only desorption, while complexes such as RuPbpz (E1/2 > 1.62 V vs Ag/AgCl) displayed only chemical decomposition. Comparing isomers of 4,4'- and 5,5'-disubstituted-2,2'-bipyridine ancillary ligands, a dramatic increase in the rate of desorption of the Ru(III) complexes was observed for the 5,5'-ligands. Nanoscopic indium-doped tin oxide thin films (nanoITO) were also sensitized and analyzed with cyclic voltammetry, UV–vis absorption spectroscopy, and X-ray photoelectron spectroscopy, allowing for further distinction of desorption versus ligand-substitution processes. Desorption loss to bulk solution associated with the planar surface of FTO is essentially non-existent on nanoITO, where both desorption and ligand substitution are shut down with RuP4OMe. Finally, these results revealed that minimizing time spent in the oxidized form, incorporating electron-donating groups, maximizing hydrophobicity, and minimizing molecular bulk near the adsorbed ligand are critical to optimizing the performance of ruthenium(II) polypyridyl complexes in dye-sensitized devices.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Center for Solar Fuels (UNC EFRC)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0001011
- OSTI ID:
- 1470651
- Journal Information:
- ACS Applied Materials and Interfaces, Vol. 10, Issue 26; Related Information: UNC partners with University of North Carolina (lead); Duke University; University of Florida; Georgia Institute of Technology; University; North Carolina Central University; Research Triangle Institute; ISSN 1944-8244
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
catalysis (homogeneous)
catalysis (heterogeneous)
solar (photovoltaic)
solar (fuels)
photosynthesis (natural and artificial)
hydrogen and fuel cells
electrodes - solar
charge transport
materials and chemistry by design
synthesis (novel materials)
synthesis (self-assembly)
electrochemistry
phosphonate
sensitizer
ruthenium
stability
photoelectrosynthesis
dye-sensitized
interfaces