Durability and Performance of Poly(norbornene) Anion Exchange Membrane Alkaline Electrolyzer with High Ionic Strength Anolyte

Abstract

Anion exchange polymer electrolytes enable low-temperature alkaline water electrolysis for reliable green hydrogen production. Anion exchange membrane water electrolysis (AEMWE) with alkaline electrolytes has several advantages over the proton exchange membrane water electrolysis using acid-based polymer electrolytes. The advantages include low-cost catalysts, all hydrocarbon non-fluorinated polymer membrane, and low-cost cell components. Long-term durability of AEMWEs in high pH operation has been challenging, although there have been significant performance improvements. AEMWE operated at low hydroxide anolyte provides improved chemical stability.In this study, an understanding of the high ionic-strength anolyte is provided along with demonstration of the AEMWE performance and durability. Anion exchange poly(norbornene) solid polymer electrolytes show high-performance, durable membrane electrode assemblies for alkaline electrolysis. Covalently bonded, self-adhesive solid polymer ionomers were used in electrodes for durable electrolysis. Hydration problem with the low pH alkaline anolyte in dry-cathode AEMWE is presented. The effect of anolyte concentration and mobile cations on the cathode electrolysis performance using a low hydroxide anolyte was investigated. High ionic strength anolyte was prepared by changing the mobile cation concentration while maintaining a constant anolyte pH. The mechanism of cathode hydration improvement through use of a high ionic strength anolyte is presented. Long-term durability with the optimal high ionic strength electrolyte is discussed.