Understanding the Durability and Degradation of Gas Diffusion Electrodes for Carbon Dioxide Electrolysis in Alkaline Media

Abstract

Anthropogenic CO2 emissions present an immediate and unprecedented threat to our planet. Electroreduction of CO2 (ECO2RR) offers the dual benefits of reducing CO2 emissions from point sources and producing valuable chemicals such as CO, formic acid, and ethanol in a carbon-neutral manner.1,2 Over the past decade, a significant body of research has focused on improving the product selectivity and activity of CO2RR catalysts, but studies regarding long-term stability and durability of these electrocatalytic systems have been rare.3 To date, only a few studies have reported performance durations exceeding 100 hours, and even fewer have reported on possible mechanisms underlying decrease in performance and system failure.4 Techno-economic analyses suggest a lifetime of 3000 hours or greater is needed for economically feasible ECO2RR systems5. Progress in this area will be crucial for further development of ECO2RR technology.This poster will report key findings from our comprehensive review of durability testing in ECO2RR systems, specifically common degradation mechanisms. We will focus primarily on gas diffusion electrodes (GDEs), used in high-performance alkaline flow and membrane electrode assembly systems. In our alkaline flow system, we have observed a number of degradation mechanisms consistently impacting our GDEs including leaching and carbonate formation. Characterization of used GDEs, including SEM, EDX, XRD, and Micro-CT, was employed to understand how operating at high current densities (–100 to –200 mA cm-2) in alkaline electrolytes impacts structure and chemical composition.Secondly, this poster will outline ways in which we have attempted to improve durability in our GDEs. By applying insights from the literature to studies carried out in our flow system, we have evaluated changes in the electrolyte, electrode substrate, catalyst deposition method, and catalyst ink binder to optimize GDE design and augment durability. Lastly, we will report on accelerated durability and stress testing (ADT/AST) methods that we have developed, and our findings from implementation of these methods in our system. These accelerated procedures can be broadly applied to highly active (≥200 mA cm–2), lab-scale ECO2RR systems to determine long-term stability and degradation modes in shorter timeframes. Acknowledgement We gratefully acknowledge financial support from Shell’s New Energies Research & Technology - Dense Energy Carriers Program and I2CNER.