Hydrogen at Scale Using Low-Temperature Anion Exchange Membrane Electrolyzers

Abstract

Among the two commercial low-temperature electrolyzers, alkaline liquid electrolyzers (AELs) and proton exchange membrane electrolyzers (PEMELs), AELs have the largest market share. They are durable, with a system lifetime of 30–40 years. The principal issues are high ohmic resistance and thicker diaphragms lowering voltage efficiency and limiting current density performance. In addition, the use of corrosive liquid electrolytes increases system-level costs. Typically, the pressure ranges available are low and hence the need for additional compression technologies for hydrogen storage and transportation. In comparison with AELs, PEMELs have higher current density and voltage efficiency, fast dynamic response, compact cell design, and the ability to be pressurized. However, the principal disadvantage of PEMELs is their costly platinum-group metals and titanium-based stack components. Anion exchange membrane electrolyzers (AEMELs) combine the features and advantages of AELs and PEMELs. In AEMELs, denser hydroxide ion exchange membranes replace the microporous diaphragm separators of AELs, thus enabling hydrogen pressurization and operation at high current density. In addition, they replace precious metals in PEMELs with earth-abundant, inexpensive materials, making them more affordable and scalable.