Solid oxide electrolysis (SOXE) provides a high efficiency pathway to electrolyze steam, carbon dioxide, or a mixture of the two to produce hydrogen, carbon monoxide, or synthesis gas respectively. Irrespective of the cell design, instability of fuel electrode is a source of performance degradation.

Traditionally, solid oxide electrolysis stacks use nickel–zirconia or nickel–ceria composite cathode to reduce the oxidized species. Nickel based electrodes are susceptible to oxidation by the feed gas (CO₂ or steam) at the inlet conditions and are often irreversibly damaged unless reducing gas (carbon monoxide or hydrogen) is also present. This necessitates a complex, recycle loop that introduces a fraction of the product gas to the inlet. The gas recycle approach was successfully implemented for OxEon’s SOXE stack that is operating on Mars to produce high purity oxygen using atmospheric carbon dioxide. Under a NASA SBIR program, OxEon investigated a combination of materials and engineering solutions to improve redox tolerance of the nickel based cathode so that 100% dry CO₂could be fed directly into a stack without damaging the electrode. The redox tolerance through the use of a modified nickel based cathode composition has been demonstrated. Button cells and stacks have been shown to tolerate complete oxidation of Ni to NiO, with performance recovery occurring in a matter of minutes using only the CO generated by the electrolysis reaction to re-reduce the cathode. The redox tolerant stack was also demonstrated to show improved coking tolerance over the traditional cathode material. This feature allows higher conversion of CO₂enabling increased O₂ production. Tests are ongoing to evaluate redox tolerance for steam electrolysis.