Future NASA missions require high efficiency, lightweight, long life, and maintenance-free water electrolyzer technologies to generate oxygen and/or hydrogen for energy storage, propulsion, life-support systems, cabin-oxygen replenishment, and zero-g science activities. International Space Station, future Lunar and Martian Outposts, and future exploration vehicles require high efficiency electrolyzers to improve their operational capabilities for long and complex missions. The oxygen evolution reaction is the limiting step due to non-optimal electrocatalyst structure. State-of-the-art electrocatalysts do not meet MEA efficiency and lifetime requirements for NASA applications. Advanced electrocatalysts are needed. In the Phase I, Lynntech manufactured a binary nanoparticle surface decorated mixed oxide electrocatalyst with the optimal microstructure and demonstrated an MEA efficiency of >90% (i.e., an electrolysis potential of 1.358 V/cell) at 200 mA/cm2. In the Phase II program, Lynntech will investigate different catalyst morphologies to improve the lifetime. In addition, ternary transition metal oxides will be incorporated into the mixed oxide to further increase the efficiency and lifetime. The applicability of this advanced catalyst to different membranes will be investigated. Nanocomposite membranes with low hydrogen gas cross-over will be manufactured and tested. A short electrolyzer stack will be assembled with the optimized components, tested and delivered to NASA.