Date of Award

Fall 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Brudvig, Gary

Abstract

The development of devices for renewable energy generation and storage is becoming increasingly important as climate challenges persist. This dissertation focuses on the investigation of materials that are used for photoelectrochemical water splitting. Photoelectrochemical cells (PECs) are composed of semiconducting materials that can absorb solar radiation and store it in the form of chemical bonds or for solar fuel generation. Wide bandgap semiconductors are often incorporated in these devices to be photoexcited by solar radiation and remain in a charge separated state long enough to generate a current. In an effort to increase efficiency, metal oxides have been functionalized with dyes to absorb more of the visible spectrum and increase efficiency. Beyond metal oxides, conductive metal-organic frameworks (MOFs) are relatively new in the application of PECs. MOFs are extended structures composed of building blocks of metal nodes and organic linkers. Their tunability and porosity present great opportunities for the control and design of further conductive MOFs. By changing the structural geometry, elemental composition, or aromaticity, there are many variables to tune to increase photoconductivity. A conductive MOF photoanode is presented. Terahertz (THz) spectroscopy is an excellent tool to investigate charge transport in these materials. THz acts as a contact-free probe of conductivity as it is attenuated in proportion to mobile charges. Spectroscopy has benefits over direct current probe techniques when measuring conductivity as there is no mechanical resistance and it can be utilized at subpicsecond timescales. Photoconductivity is measured using optical pump, THz probe (OPTP) and time-resolved THz spectroscopy (TRTS). THz is a powerful tool to study semiconducting materials and the following results may provide insight into the next generation of photoanode materials for solar energy conversion.

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