(524a) Porous Solid Electrolytes for Efficient CO2 Electrolysis

The electrochemical CO₂ reduction reaction (CO₂RR) can convert CO₂ from industrial emissions or air into valuable products, such as formic acid, ethylene, or ethanol. However, conventional CO₂ reduction electrolyzers typically employ liquid-based electrolytes, resulting in expensive post-synthesis purification steps to recover the product. Porous solid electrolyte (PSE) reactors can potentially address these product separation limitations, but the current PSEs rely on solid electrolyte particles and exhibit poor long-term stability. Here, we report on the development of novel PSEs for CO₂ electrolyzers. First, we describe a free-standing and highly conductive PSE layer for CO₂ electrolysis produced by combining ion exchange particles with sulfonated polysulfone as a binder. The resulting PSE achieved an ionic conductivity as high as 10.4 mS/cm while maintaining excellent mechanical properties. We found that optimized PSEs exhibited superior conductivities compared to commercial particles and excellent stability, enabling continuous operation of a solid-state CO₂RR for over 220 hours. In second approach, we demonstrate that surface-functionalized silica particles can be used as PSEs for CO₂ electrolysis. We prepared surface functionalized particles ranging in size from 20 nm to 40 µm and functionalized with sulfonate groups. We found that decreasing particle size produced particles resulted with the highest ionic conductivity, as high as of 5.31 x 10^-2 S cm^-1, but the smallest particles resulted in clogging of the flow cell. The silica particles achieved greater than 90% selectivity for formic acid in a CO₂ reduction reactor. This work provides insight into the design of PSEs for CO₂ electrolysis for the production of pure liquid products.