Date of Award

Fall 2022

Project Type

Dissertation

Program or Major

Chemistry

Degree Name

Doctor of Philosophy

First Advisor

Christine Caputo

Second Advisor

Roy Planalp

Third Advisor

Rudi Seitz

Abstract

The energy shortage and the global climate change have drawn great attention from humankind. Scientists worldwide are trying to find a green energy pathway. Shifting from a primarily fossil fuel-based energy economy to a solar fuel derived energy economy is a promising solution to eliminate greenhouse gases emissions and to protect our climate.

Electrocatalysis and photocatalysis are two practical strategies devised to generate solar fuels. Catalysis using transition metal complexes have been intensively investigated as their structures can be precisely controlled allowing an understanding of the mechanism of the catalytic reactions. This ultimately allows improvement of the activity can be achieved through rational synthetic design.

Cobalt polypyridyl complexes have been extensively studied as both photo- and electrocatalytic homogeneous catalysts for the hydrogen evolution reaction (HER). When anchored onto a metal oxide surface, the stability of the anchoring group is often implicated in limiting catalytic turnover due to catalyst release. This dissertation includes the synthesis of a tetrapyridyl cobalt (II) complex with an appended linker terminated by a silatrane moiety that can convert to a silane anchoring group in the presence of a metal oxide electrode surface. Structural and electrocatalytic characterization of this catalyst has been performed which demonstrated successful synthesis and confirmed molecular integrity following anchoring. The strategy of silatrane immobilization was used with mesoporous titanium dioxide (TiO2) on fluorine doped tin oxide (FTO) conductive glass electrodes and was shown to perform long lived heterogeneous electrocatalytic hydrogen evolution. In addition, the siloxane catalyst was anchored on TiO2 nanoparticles with co-immobilization of a Ru (II) photosensitizer for visible light driven hydrogen evolution in a hybrid photocatalytic system.

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