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Thesis Format

Alternative Format

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Andrew N Hrymak

Abstract

The increasing global concerns over climate change and environmental degradation have intensified the search for sustainable and efficient energy solutions. Among various alternatives to traditional fossil fuel-based power systems, proton exchange membrane fuel cells (PEMFCs) have gained significant attention due to their high efficiency, low emissions, and ability to generate clean energy. However, one of the critical challenges in fuel cell technology is the development of cost-effective, durable, and highly conductive bipolar plates (BPs), which play a vital role in the overall performance and longevity of PEMFCs.

This research aims at developing highly filled fractal graphene-based vinyl ester polymer composites suitable for applications such as bipolar plates in proton exchange membrane fuel cells. There is a growing interest in finding an alternative to the internal combustion engine because of the rising impacts of Green House Gases on climate change. Fuel cells are a clean, safe, and efficient power source that transforms chemical energy stored in hydrogen and oxygen directly into electrical energy.

The novel material investigated in this work is fractal graphene, an ultra-high purity turbostratic form of graphene. The graphene used in this work is produced in a novel, one-step, highly efficient, gas-phase and environmentally friendly process, which yields pristine graphene nanosheets. The study reviewed various methods to formulate different kinds of thermoset resin/filler systems. These approaches were further investigated at high carbon filler concentration to develop polymer composites suitable for BPs. The polymer composites were developed by compression molding of vinyl ester as a binder and conductive fillers natural graphite, synthetic graphite, carbon black, and fractal graphene. The study investigates the effects of various formulations of these carbon fillers on the electrical and mechanical properties of vinyl ester polymer composites.

The addition of fractal graphene from 0 wt.%, to 0.09 wt.% while maintaining 50 wt.% total carbon, predominantly natural graphite, significantly enhances both through-plane and in-plane conductivity compared to other formulations of the named carbon fillers. A highly filled system containing 70 wt.% carbon fillers was also investigated. The addition of 0.6 wt.% fractal graphene alone led to an 82% increase in in-plane electrical conductivity and a 133% improvement in through-plane electrical conductivity, compared to the formulation without graphene. In addition to exhibiting excellent electrical properties, these highly filled composites possessed impressive flexural modulus, strength, and tensile strength.

Summary for Lay Audience

The increasing demand for sustainable and clean energy solutions has driven significant interest in Proton Exchange Membrane Fuel Cells (PEMFCs). As an efficient and environmentally friendly technology, PEMFCs generate electricity through the electrochemical combination of hydrogen and oxygen, with water being the only byproduct. This makes them a promising alternative to conventional internal combustion engines, which contribute significantly to greenhouse gas emissions. However, one of the key challenges in PEMFC technology lies in the development of cost-effective and high-performance Bipolar Plates (BPs), which are essential for conducting electricity, distributing gases, and providing mechanical integrity within the fuel cell.

To tackle these challenges, this study develops advanced composite materials for BPs. Composites are materials made by combining different substances—in this case, a vinyl ester resin (a type of plastic) mixed with conductive fillers like graphite, carbon black, and Fractal Graphene (FG). FG is a novel and unique form of graphene made through a clean and efficient process called gas-phase detonation. It offers excellent electrical and mechanical properties, even in small amounts.

By combining FG with other carbon fillers, the research is trying to achieve materials that are lightweight, highly conductive, and strong, making them ideal for fuel cells. These improved composites could make fuel cells more affordable and efficient, paving the way for eco-friendly energy solutions.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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