Semester of Graduation

Summer 2025

Degree

Master of Science in Chemical Engineering (MSChE)

Department

Cain Department of Chemical Engineering

Document Type

Thesis

Abstract

The electrochemical reduction of CO₂ using membrane electrode assembly (MEA) cells has emerged as a promising approach for carbon capture and conversion into valuable products. This study investigates the degradation mechanisms of anion exchange membranes (AEMs) in CO₂ reduction applications, focusing on Sustainion X37-50, PiperION, and FAA-3-50. The research analyzes the impact of chemical and mechanical degradation on membrane performance, highlighting key stability challenges in long-term operation. Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS) were employed to monitor functional group stability and ionic conductivity loss over extended operation. The results indicate that hydroxide-induced degradation leads to nucleophilic substitution and Hofmann elimination, significantly reducing membrane conductivity over time. Mechanical tests further reveal structural weakening due to prolonged electrochemical cycling, with Young’s modulus and tensile strength declining substantially after extended exposure. To address the limitations of AEMs, this work explores the feasibility of non-charged porous membranes, such as polyvinylidene fluoride (PVDF), as alternatives for CO₂ electrolysis. Comparative Faradaic efficiency (FE) analysis between AEMs and non-charged membranes demonstrates that while AEMs enhance C₂ product formation, porous membranes can maintain similar selectivity for liquid-phase products. The reduced ethylene production with PVDF membranes suggests a shift in local reaction conditions and charge transport mechanisms, altering CO₂ reduction pathways on the Cu catalyst. Unlike anion exchange membranes (AEMs), which degrade under highly alkaline conditions due to chemical attacks on their functional groups, porous membranes are more resistant to degradation since they do not rely on fixed charged sites for ion conduction. Their ability to allow electrolyte penetration ensures sufficient ionic conductivity while maintaining structural integrity over prolonged use. This makes them a potential low-cost and durable solution for scaling up CO₂ electrolysis, particularly in systems where membrane degradation limits efficiency. Additionally, combining porous membranes with catalysts that enhance CO₂ solubility and reaction selectivity could lead to more efficient electrochemical conversion systems. As research progresses, these membranes could enable the development of more durable and commercially viable CO₂ electrolyzers, helping bridge the gap toward large-scale carbon utilization technologies.

Date

7-7-2025

Committee Chair

Flake, John C.

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