Recent advances in membranes and ionomers for high and low-temperature electrochemical hydrogen pumps

The electrochemical hydrogen pump (EHP) is a promising technology for simultaneous hydrogen purification and compression with minimal greenhouse gas emissions. The membrane electrode assembly (MEA), consisting of catalyst layers (catalyst + ionomer binder, CL) and proton exchange membrane (PEM), plays a pivotal role in the EHP.  While existing reviews have predominantly focused on the catalysts used in EHPs, there is a noticeable research gap in understanding ionomer properties. This review addresses this gap by focusing on the recent advances in ionomers and PEMs for the EHP, emphasizing their distinct characteristics. Additionally, we discuss the ionomer and PEM considerations in low-temperature (LT) and high-temperature (HT) EHP systems.