Date of Award

7-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical and Chemical Engineering and Sciences

First Advisor

Michael Freund

Second Advisor

Nasri Nesnas

Third Advisor

Mary Sohn

Fourth Advisor

Jonathan Whitlow

Abstract

Currently, there is a great need for research and development on new sources of energy in order to meet energy demands in a clean, efficient, sustainable, economical and environmentally friendly way. A system that promises to meet these requirements is water splitting through artificial photosynthesis, generating hydrogen and oxygen, effectively storing light energy in the form of fuel such as H2. One main limitation in artificial photosynthesis is that the membrane must be able to conduct the ions involved in redox reactions, as well as the electrons/hole carriers produced by light absorption, while being mechanically stable and optically transparent. No one material fulfills all of these demands to date, and as such a composite is desired. Due to the conditions the membrane is exposed to, the composite should also be homogeneous on the nanoscale, electronically tunable and impermeable to gases. This research seeks to develop such composite membranes, looking at tuning the electronic and ionic characteristics of the membrane through incorporation of electrical conductors such as PEDOT:PSS or GO, and ionic conductors such as Nafion and a novel anionic exchange membrane. The morphology, thickness, and conductivity measurements were taken and compared to previous reports. It has been concluded that these composite membranes have attractive ionic, electronic and physical properties for artificial photosynthetic applications. Secondly, this research also focuses on the creation of a composite bipolar membrane that could be used in an artificial photosynthetic device, allowing a pH gradient to exist in the system between the oxidation and reduction reaction cells. Key performance characteristics such as pH gradient stability, electronic and ionic conductivity were monitored, and compared to figure of merits in the literature. It was found that the composite films explored are able to meet the figures of merit outlined for these integrated energy systems. The findings of this study can help in manufacturing, utilization and evaluation of such a bipolar membrane for commercial use.

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