Semester of Graduation

Fall 2023

Degree

Master of Science in Chemical Engineering (MSChE)

Department

Chemical Engineering

Document Type

Thesis

Abstract

Annually, over 35 billion metric tons of carbon dioxide (CO2) are emitted into Earth’s atmosphere. The accumulated CO2 emissions in the atmosphere over the last century drive climate change. CO2 electroreduction (CO2ER) is an emerging technology that aims to recycle carbon emissions from the industrial sector by using CO2, H2O, and electricity as a feedstock to produce ethylene (C2H4) at current densities as high as 1 A cm-2 and Faradaic efficiencies (FE) of 60%. However, CO2 electrolyzers currently demonstrate poor durability at industrially relevant current densities (greater than 200 mA cm-2), with the majority of CO2 reduction studies not exceeding 20 hours. Discussion related to the timing and causes of CO2ER membrane electrode assembly (MEA) cell failures is lacking, even among long-term studies.

This work considers the effects of different polymer binders on GDE surface hydrophobicity, and the resulting impact on CO2 electrolyzer durability. Polymer binders are commonly employed to affix Cu electrocatalyst to gas diffusion electrodes (GDEs) in CO2 MEA electrolyzers, and have been shown to impact GDE surface hydrophobicity. Five polymers (PVDF, PTFE, Nafion, XC-2, XA-9) are employed as binders in GDEs in to-failure durability tests. In-operando measurements of reactor products, feed pressures, and flow rates are used to determine the impact polymer binders have on product selectivity and carbonate salt formation. A clear pattern of potassium carbonate salt precipitation based on the hydrophobicity of the GDE is observed. Additional layers containing carbon and polymer binder are also employed to enhance CO2 electrolyzer durability.

Date

11-14-2023

Committee Chair

John C. Flake

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