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 IrO₂ and Pt that are nominally stable under the locally acidic conditions of the ionomer. Alkaline-exchange-membrane (AEM) electrolyzers in principle offer the performance of commercialized PEM electrolyzers with the ability to use earth-abundant catalysts and inexpensive bipolar plate materials. I will present our fundamental work in understanding earth-abundant water-oxidation catalysts, including the use of integrated reference-electrode device architectures and cross-sectional materials analysis, as well as progress in building high-performance AEM electrolyzers. Baseline systems operate at 1 A·cm^-2 in pure water feed at < 1.9 V at a moderate temperature of ~70 °C using either IrO₂ or Co₃O₄ anode catalyst layers, PiperION alkaline ionomers, and stainless steel porous transport layers. These devices, however, degrade rapidly compared to PEM electrolyzers. The voltage profile corresponding to degradation has intial fast (~10 mV/h) and steady-state slow components (~1 mV/h), which we link to chemical and structural changes in the ionomer catalyst reactive zone. I will discuss these processes in electrolyzer devices and in model systems that are correlated with this performance loss, as well as present promising new strategies we have developed to mitigate degradation using novel ionomers and electrode catalyst compositions and architectures.