Synthesis of Oligomeric Ruthenium Polypyridyl Dyes and Liquid Imidazolium Zwitterions for Improved Energy Generation and Storage
Open Access
- Author:
- Rothenberger, August
- Area of Honors:
- Chemistry
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Thomas E Mallouk, Thesis Supervisor
Raymond Lee Funk, Thesis Honors Advisor
Robert John Hickey, III, Faculty Reader - Keywords:
- water splitting
oligomer
energy
zwitterion
polymer electrolyte - Abstract:
- Water-splitting, dye-sensitized photoelectrochemical cells (WS-DSPECs) use molecular sensitizers to harvest solar energy and facilitate the catalytic reactions necessary to generate hydrogen and oxygen from water. Photostability of sensitizers and cross-surface hole diffusion on the electrode surface are two properties that have received recent attention as key limiting factors in the efficiency of WS-DSPECs. We have synthesized a novel oligomeric ruthenium polypyridyl dye that has dramatically improved adhesion to TiO2 electrodes at pH 4.8 and pH 7.8. Long-term stability of the oligomer was observed at high pH ranges traditionally incompatible with monomeric dyes. The apparent hole diffusion constant, Dapp, of the oligomer was an order of magnitude higher than the monomeric dye, indicating the oligomer’s effectiveness in enhancing cross-surface transport of oxidizing equivalents to water-splitting catalytic sites. These results demonstrate that use of oligomeric dyes is an effective strategy in designing high-stability chromophores for WS-DSPECs. In the pursuit of solid-state, solvent-free lithium ion batteries, polyelectrolytes have gained considerable attention. Zwitterions with large static dielectric constants have been shown to dramatically increase ionic conductivity in polyelectrolytes by enhancing ion dissociation from the polymer backbone. Low-melting temperature zwitterions mitigate complications caused by addition of a solid molecule to the conductive polymer system. Additionally, it is possible to directly measure the static dielectric constant, 𝜀𝑠, of the pure liquid zwitterions at room temperature. We have successfully synthesized two imidazolium sulfonate zwitterions, OE2ImPS and OE2ImBS, the latter of which is a novel molecule, which display glass transitions well below room temperature (Tg = -9.75 and -10.75, respectively) and exceptionally high static dielectric constants (𝜀𝑠 = 204.8 and 205.1 at 20 °C). These findings indicate that the synthesized zwitterions should be highly effective at increasing ionic conductivity in polyelectrolytes.