Date of Award

2019-01-01

Degree Name

Doctor of Philosophy

Department

Chemistry

Advisor(s)

Geoffrey B. Saupe

Abstract

The wide band gap layered semiconductors potassium titanium niobium oxide (KTiNbO5) and potassium hexaniobate (K4Nb6O17) along with a metal co-catalyst can be been used to generate hydrogen fuel from water. However, ultraviolet light is required, which limits their utility in solar energy conversion. Modification of these types of semiconductors can sensitize them to visible light, providing a promising way to produce clean, renewable hydrogen (H2) fuel. Many photocatalysts suffer from poor H2 production efficiencies under visible light, due to inadequate and unstable sensitizers, resulting in photocatalysts that fail quickly.

In this research, several new high surface area dye sensitized nanocomposites were synthsized with a unique nanosheet restacking method for use in solar energy conversion. The nanocomposites are porous and are internally sensitized by high loadings of visible light photosensitizer molecules. Tris(2,2'-bipyridyl)ruthenium(II), abreviated as Ru(bpy)32+, was successfully incorporated into porous KTiNbO5 and K4Nb6O17 frameworks. The resulting nanocomosites are very stable under visible light irradiation and sensitizer loadings were exceptionally high, which produced very efficient catalysts. The long-term stability and high dye content in these structures make these nanomaterials ideal candidates for generating photocatalytic H2 fuel from water. The strategy demonstrated here is general enough to be used for different sensitizers and other layered oxides. 5,10,15,20-tetrakis(1-methyl-4-pyridinio) porphyrin dye, or TMPyP4+ was also successfully incorporated into a restacked porous oxide to be used as H2 evolution photocatalyst from water. The full chemical, morphological, and photophysical characterization were carried out of all the materials synthesized in this work. In addition, the use of exfoliated and restacked layered materials to create new fast kinetics ion-exchangeable materials were explored.

Language

en

Provenance

Received from ProQuest

File Size

155 pages

File Format

application/pdf

Rights Holder

Tahmina Akter

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Chemistry Commons

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