The production of hydrogen fuel via solar water splitting is an important carbon-neutral strategy for the development of renewable resources and has sparked great interest in the scientific community. Hydrogen production efficiencies for supramolecular photocatalysts of the architecture [{(TL)2Ru(BL)}2RhX2]5+ (BL=bridging ligand, TL=terminal ligand, X=halide) are among the highest reported in deoxygenated organic solvents, but do not function in air-saturated aqueous solution due to quenching of the metal-to-ligand charge transfer (MLCT) excited-state under these conditions. Herein, we report the groundbreaking use of polyelectrolytes to increase efficiency of supramolecular photocatalysts in solar hydrogen production schemes under aqueous aerobic conditions. The new photocatalytic system incorporates poly(4-styrenesulfonate) (PSS) into aqueous solutions containing [{(bpy)2Ru(dpp)}2RhCl2]5+ (bpy = 2,2'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine). PSS has a profound impact on photocatalyst efficiency, increasing hydrogen production over three times that of deoxygenated aqueous solutions alone. Hydrogen photocatalysis proceeds even under aerobic conditions for PSS containing solutions, an exciting consequence for solar hydrogen production research.
Thermodynamics of binding due to intermolecular interactions between Ru,Rh,Ru photocatalysts and polyelectrolytes was probed using isothermal titration calorimetry (ITC). ITC studies reveal the driving forces of aggregate formation, providing new insight into the intermolecular forces that lead to increased photocatalytic efficiency and stability in the presence of water soluble polymers.
Synthesis and characterization of a novel supramolecular photocatalyst having hydrophilic terminal ligands are reported. Addition of sulfonated terminal ligands into a Ru,Rh,Ru photocatalyst has a significant impact on the excited-state properties of the complex. The new complex demonstrates increased solubility and hydrogen production efficiency in aqueous solutions. Hydrogen production is observed even under aerobic conditions for the new complex, a stark contrast to the hydrophobic analog in organic solvents.
The synthesis, characterization, and electropolymerization of a chromophore-catalyst assembly having vinyl-substituted terminal ligands to create robust water reduction photocatalysts on wide-bandgap semiconductors is reported. The polymeric photocatalysts are expected to show increased stability over a wide pH range and increased photostability compared to chromophore-catalyst assemblies that employ carboxylic or phosphonic acid groups to adsorb the photoreactive catalyst to the metal oxide surface. / Ph. D. / The production of H₂ fuel from water using sunlight is an important carbon-neutral strategy for the development of renewable resources and has sparked great interest in the scientific community. H₂ production efficiencies for light-activated catalysts of the architecture [{(TL)₂Ru(BL)}₂RhX₂]⁵⁺ (BL=bridging ligand, TL=terminal ligand, X=halide) are among the highest reported in deoxygenated organic solvents, but do not function in air-saturated aqueous solution due to deactivation of the catalyst under these conditions. Herein, we report the groundbreaking use of water soluble polymers to increase efficiency of light activated catalysts in solar H₂ production schemes in air-saturated water. The new photocatalytic system incorporates poly(4-styrenesulfonate) (PSS) into aqueous solutions containing [{(bpy)₂Ru(dpp)}₂RhCl₂]⁵⁺ (bpy = 2,2'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine). PSS has a profound impact on the efficiency of the light activated catalyst, increasing H₂ production over three times that of deoxygenated aqueous solutions alone. H₂ production proceeds even in air-saturated water for PSS containing solutions, an exciting consequence for solar hydrogen production research.
Interactions between Ru,Rh,Ru light activated catalysts and polyelectrolytes were probed using isothermal titration calorimetry (ITC). ITC studies reveal the driving forces of aggregate formation, providing new insight into the intermolecular forces that lead to increased efficiency and stability in the presence of water soluble polymers.
Synthesis and characterization of a novel light activated catalyst having hydrophilic terminal ligands are reported. Addition of water soluble terminal ligands into a Ru,Rh,Ru light-activated catalyst has a significant impact on the excited-state properties of the molecule in aqueous solution. The new molecule demonstrates increased solubility and H₂ production efficiency in aqueous solutions. H₂ production is observed even under aerobic conditions for the new molecule, a stark contrast to the hydrophobic analog in organic solvents.
The synthesis, characterization, and polymerization of a new light activated catalyst on a metal oxide surface is reported. The polymeric light-activated catalysts are expected to show increased stability over a wide pH range and increased stability compared to light-activated catalysts that employ carboxylic or phosphonic acid groups to adsorb the catalyst to the metal oxide surface.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/86198 |
| Date | 08 June 2017 |
| Creators | Canterbury, Theodore Richard |
| Contributors | Chemistry, Moore, Robert Bowen, Gibson, Harry W., Deck, Paul A., Arachchige, Shamindri Meetiyamulla |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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