Flexibly fuelled reversible solid oxide cells based on ceria-nickel fuel electrodes support

High-temperature solid oxide electrolysis, including both steam and CO 2 electrolysis, shows strong promise for renewable fuel production thanks to its flexibility, modular design, and ability to utilise industrial waste heat, thereby enhancing overall efficiency. Its capability to operate reversibly further increases its value for energy transition applications, particularly in the storage and transport of sustainable fuels. This study focuses on developing an electrode material for reversible solid oxide cells that can preserve active nickel catalytic sites even under highly oxidising conditions typical of steam and CO 2 electrolysis. The electrodes support, composed of nickel as the catalyst and ceria as an oxygen buffer, was fabricated through co-sintering. It demonstrated effective performance in fuel-cell mode with internal methane reforming, reaching power densities up to 0.71 W cm −2 . During steam electrolysis, current densities of −2.67 A cm −2 were achieved at 775°C under thermoneutral conditions. In co-electrolysis mode, it reached −0.56 A cm −2 at 1.30 V and 750°C. Thermal analysis indicated safe operation up to 750°C due to changes in expansion behaviour at higher temperatures. These results highlight ceria's role in maintaining oxygen vacancies and mixed conductivity, supported by X-ray photoelectron spectroscopy and microstructural analysis showing enhanced triple-phase boundary formation.