10:45 AM - EN11.01.02
Characterizing Degradation Mechanisms in Gas Diffusion Electrodes for the Electrochemical Reduction of Carbon Dioxide
Emiliana Cofell1,Uzoma Nwabara1,Saket Bhargava1,Danielle Henckel2,Zachary Park1,Paul Kenis1
University of Illinois at Urbana-Champaign1,National Renewable Energy Laboratory2
Show Abstract
The electrochemical reduction of CO2 offers the dual benefits of recycling CO2, thereby mitigating emissions, and producing intermediates for valuable fuels and chemicals such as CO, formic acid, ethylene, and ethanol in a carbon-neutral manner.1,2 Previous research has focused on the application of gas diffusion electrodes (GDEs) in CO2 reduction systems, which has enabled the conversion of CO2 into products at a high rate.3,4 Despite these GDEs requiring a lifetime of at least 3000 hours for economic feasibility, their durability has not been studied widely.4,5 In fact, many GDEs studied to date show declining performance over time, the causes of which have not been determined. Progress in this area, in particular with respect to understanding GDE degradation mechanisms, will be crucial for further development of CO2 reduction technology.
This presentation will discuss post-testing changes in GDE cathode surface morphology and composition as a function of electrolyte composition and applied current density/potential. We investigated these changes via a variety of surface and bulk characterization techniques (SEM, EDS, Micro-CT, XRD). This approach identified degradation mechanisms including carbonate deposit formation, surface passivation, and catalyst layer restructuring, leading to loss of catalyst availability. In particular, we determined that a highly alkaline electrolyte, although beneficial for achieving high current densities and efficiency for CO production, causes the rapid formation of carbonate deposits on the GDE surface due to high local pH at the reaction interface.7 The extent of carbonate deposit formation depends heavily on electrolyte cation identity and concentration. We also explored the impact of potential cycling on the catalyst later, noting significant restructuring and loss of catalyst layer when more positive potentials are repeatedly applied to the cathode. By using a combination of materials characterization techniques and electrochemical methods, we are able to image the evolution of the GDE surface, determine which conditions lead to loss of catalyst surface area, and better understand how to develop long-lasting electrodes for electrochemical reduction of CO2 to value-added chemicals.
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