Kibria, Md GolamRashid, Mohsina2024-04-032024-04-032024-03-26Rashid, M. (2024). Development of bilayer ionomer coatings for enhanced carbon dioxide electrolysis towards multi-carbon products (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.https://hdl.handle.net/1880/118350https://doi.org/10.11575/PRISM/43192In the realm of carbon neutrality, electrochemical CO2 reduction (eCO2R) stands as a pivotal technology for converting carbon dioxide into valuable multi-carbon (C2+) products, such as ethylene (C2H4) and ethanol (C2H5OH). Despite significant strides in achieving high Faradaic efficiency (FE) at industrial-scale current densities, persistent challenges like cathode flooding and (bi)carbonate salt accumulation in alkaline electrolytes continue to pose fundamental concerns. This study addresses these challenges by leveraging ion-conducting polymers (ionomers) to tailor the micro-environment mitigating cathode flooding and (bi)carbonate crossover and thus, enhance the local CO2 availability in eCO2R. Exploring the impact of cation and anion exchange ionomer layers, specifically Nafion and Sustainion XA-9, reveals that a cation infused ultra-thin bilayer configuration significantly reduces cathode flooding and salt accumulation by approximately 58%, outperforming commercial anion exchange membranes (AEM). Initially, a Single Layer Ionomer (SLI) using Sustainion XA-9 proves effective in mitigating cathode flooding due to the back convection of the thin hydrophobic cathode. Despite an impressive initial partial current density towards C2+ products (jC2+) of ~280 mA/cm2, challenges arise concerning (bi)carbonate formation and CO2 loss. Introducing an additional Nafion layer mitigates (bi)carbonate crossover, attributed to controlled OH- and K+ ion transport facilitated by the Nafion layer. However, the introduction of a Bilayer Ionomer (BLI) configuration results in lower C2+ selectivity due to insufficient OH- diffusion to establish the alkaline micro-environment essential for C2+ reaction pathways. Subsequently, incorporating cation infusion in this bilayer ionomer system (Cation Infused Bilayer Ionomer or CIBLI) proves beneficial, promoting C-C bond formation and creating a favorable micro-environment for selective C2+ product generation. The CIBLI system achieves a substantial high partial current density of approximately ~284 mA/cm2 towards C2+ products, maintaining stable eCO2R performance over 24 hours. The scalability of the directly deposited ultrathin CIBLI configuration offers a minimal conversion energy of 117 GJ/ton for C2+ products with an electrolyzer energy efficiency (EE) of 29% at 350 mA/cm2 current density. This one-step CO2 conversion process represents a promising advancement, emphasizing both efficiency and sustainability in carbon recycling technologies.enUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.CO2 ElectrolysisIonomersBilayer Ionomer CoatingMulti carbon productsPartial current densityDirectly deposited membraneCathode FloodingNafionSustainion XA-9EnergyEngineering--ChemicalEngineering--Environmentalmaster thesis