The electrolyte can be O2− conducting and/or proton(H+) conducting. The state of the art for O2− conducting yttria stabilized zirconia(YSZ) based SORFC using Ni–YSZ as the hydrogen electrode and LSM (or LSM–YSZ) as the oxygen electrode has been actively studied. Dönitz and Erdle reported on the operation of YSZ electrolyte cells with current densities of 0.3 A cm−2 and 100% Faraday efficiency at only 1.07 V. The recent study by researchers from Sweden shows that ceria-based composite electrolytes, where both proton and oxide ion conductions exist, produce high current output for fuel cell operation and high hydrogen output for electrolysis operation. Zirconia doped with scandia and ceria (10Sc1CeSZ) is also investigated as potential electrolyte in SORFC for hydrogen production at intermediate temperatures(500-750 °C). It is reported that 10Sc1CeSZ shows good behavior and produces high current densities, with suitable electrodes.