(353c) Free-Standing Porous Solid Electrolyte Layer for Efficient CO2 Electrolysis

CO₂ reduction reactors can convert carbon dioxide (CO₂) into chemical fuels, enabling sustainable processes for CO₂ reduction and chemical production. However, conventional CO₂ reduction reactors use liquid-based electrolytes and as a result require costly post-reactor purification steps. Here, we report a free-standing and highly conductive PSE layer for CO₂ electrolysis produced by combining ion exchange particles with sulfonated polysulfone as a binder. We optimized the PSE by varying both the degree of sulfonation of the binder and the binder content in the free-standing PSE while characterizing the PSE morphology and electrochemical properties. The optimized PSE achieved an ionic conductivity as high as 10.4 mS/cm while maintaining excellent mechanical properties. When used in a CO₂ electrolyzer, formate selectivity consistently exceeded 90% at current densities up to 200 mA cm^-2, and the electrolyzer maintained a cell potential close to 3.5 V over 220 hours at 100 mA cm^-2. This composite PSE therefore addresses stability and performance shortcomings of previously reported PSEs and advances the development of large-scale, energy-efficient solid-state CO₂ electrolyzers.