This paper will describe the performance of Sustainion™ membranes in CO2 and alkaline water electrolyzers. The membranes are imidazolium functionalized styrene. The membranes have a conductivity of 90 mS/cm in 1 M KOH at 60 °C . No changes in conductivity are detected after 1500 hours in 1 M KOH at 60 °C. NMR indicates that there is interesting cross linking in the polymers. The original polymers were brittle, but improvements have made them much less brittle.
We have tested the membranes for use in CO2 electrolyzers and alkaline water electrolyzers. Tests in an alkaline water electrolyzer with iron/nickel/cobalt catalysts that show a current density of 1 A/cm² at 1.9 V in 60 °C 1 M KOH. The performance is stable for 2000 hours, showing only 3-5 µV/hr degradation. Tests in a CO2 electrolyzer show 600 mA/cm2 at 3 V at 50 oC in 0.01 M KHCO3. These and other results will be discussed.