Development of Next Generation Membranes for PEM Water Electrolysis in AGC

Abstract

AGC’s FORBLUETM product family has over 70 years of experience in ion-exchange membranes (IEMs). S-SERIES, a FORBLUETM member, is a per-fluorinated sulfonic acid polymer (PFSA) membrane utilized in various electrochemical devices and industrial electrolysis. AGC’s IEM technology had a lot of experience in the chlor-alkali application and was further developed for the PEM water electrolysis industry.AGC R&D has developed S-SERIES membranes with a smaller thickness, improved reinforcement, and high ion exchange capacity (IEC) that enhanced not only an electrochemical performance but also dimensional stability.A membrane electrode assembly (MEA) was fabricated using a developed membrane with high IEC polymer (IEC 1.25 meq/g). As a result, IV characterization of a single cell with 25 cm2 electrode area at 80°C showed a significant voltage reduction compared to a commercial membrane in the PEM water electrolysis market. In addition, H2 crossover during the electrolysis was evaluated in a single cell with a 25 cm2 electrode area at 80°C and ambient pressure, and the H2 concentration in O2 at the anode side was compared at a current density of 1.0 A/cm2. The developed membrane showed 0.3 vol% H2 crossover, whereas the commercial membrane showed 0.5 vol%.Furthermore, next-generation membranes with gas recombination catalysts (GRC) and radical scavengers leading to lower gas crossover and higher chemical stability are under development. Recently, high-pressure electrolyzers have been getting more attention and the increase of H2 crossover is a concern against the lower explosive limit (LEL) for hydrogen in oxygen. In general, PFSA membranes are considered to have high chemical durability, however, F ion release is observed, that indicate that this PFSA polymer is attacked by OH radicals generated in the PEM water electrolysis system. AGC has been investigating the application of GRC and radical scavengers to the newly developed membranes. It was evaluated in a single cell with 25 cm2 electrode area at 80°C and 2.0 A/cm2. As a result, the H2 crossover and F ions release rate (FRR) were reduced compared to the membrane without both additives. The data will be presented on these improved performances.