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Solid-state alkaline water electrolysis using a pure water feed offers several distinct advantages over liquid alkaline electrolyte water electrolysis and proton exchange membrane water electrolysis. These advantages include a larger array of electrocatalyst available for oxygen evolution, no electrolyte management, and the ability to apply differential pressure. To date, there have been only a handful of reports on solid-state alkaline water electrolyzers using anion exchange membranes (AEMs), and there have been no reports that investigate loss in system performance over time. In this work, a solidstate alkaline water electrolyzer was successfully demonstrated with several types of polysulfone-based AEMs using a relatively expensive but highly active lead ruthenate pyrochlore electrocatalyst for the oxygen evolution reaction. The electrolysis of ultrapure water at 50 C resulted in a current density of 400 mA cm À2 at 1.80 V. We demonstrated that the short-term degradation of water electrolyzer performance over time was largely a consequence of carbon dioxide intrusion into the system and could be easily remedied, while longterm deterioration was a consequence of irreversible AEM polymer degradation.

Alkaline fuel cells containing anion exchange membrane electrolytes (i.e., solid-state alkaline fuel cells -SAFCs) promise to provide high power densities without platinum group metal catalysts. In the past decade, SAFC performance has improved substantially due to improvements in electrode binders that facilitate good membrane-electrode contact and ionic conductivity in the electrode layer. However, the alkaline (in)stability of AEMs is a long-standing challenge that currently precludes commercialization of this technology. To date, there have not been any satisfactory strategies or approaches to adequately assess an AEM's suitability for SAFC applications. Here, we report an all-encompassing "best practices" approach to evaluate a leading AEM candidate (poly(2,6-dimethyl 1,4-phenylene) oxide (PPO) with quaternary ammonium groups) for SAFCs. Additionally, this work reports an excellent peak power density of 294 mW cm −2 when the fuel cell was operated with hydrogen-oxygen. This high fuel cell performance was attained by painting the electrodes directly onto the membrane to minimize membrane-electrode contact resistance losses.

Lead ruthenate pyrochlore showed exceptional OER activity and stability when tested in a solid-state alkaline water electrolyzer.