Commercialized membrane electrolyzers use acidic proton-exchange membranes (PEMs). These systems offer high performance but require the use of expensive precious-metal  catalysts such as IrO 2 and Pt that are nominally stable under the locally acidic conditions. Alkaline-exchange-membrane (AEM) electrolyzers in principle offer the performance of PEM electrolyzers with the ability to use earth-abundant catalysts and inexpensive bipolar plate materials. In this talk I will present how we are building a fundamental materials science and electrochemistry understanding to create the “ultimate” H 2 -producing AEM electrolyzer technology. The AEM electrolyzer is based on fluorocarbon-free, hydroxide-ion conducting polymers, earth-abundant catalysts that accelerate the electrode reactions creating hydrogen and oxygen, and inexpensive cell and balance-of-plant components. The design is compatible with variable-current operation or integration with renewable electricity. I will trace our technology-development efforts beginning with basic catalysis and interface studies, through model devices and associated analytical-method development, and the creation of industry-relevant prototypes. I will highlight the remaining challenges centered around durability and performance that must be addressed for scale-up and commercialization and how we are working to solve these through a combination of mechanistic understanding and applied science efforts.