Steam electrolysis was studied by using La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) oxide electrolyte and it was found that H-2 formation rate obeys the Faraday's law suggesting that the transport number of oxide ion in LSGM under electrolysis condition is unity. Ni-Fe alloy cathode is highly active to electrolysis of steam, however, insertion of Ni-SDC (1:9) layer between Ni-Fe cathode and LSGM electrolyte is further effective for improving the electrolysis performance of the cell. The current density at 1.8 V was achieved values of 314 and 254 mA/cm(2) at 1073 and 873 K, respectively. The improved current density by Ni-SDC is mainly assigned to a decreased cathodic overpotential. The electrolysis efficiency which ignored the inserted heat energy, was calculated based on the formed H-2 amount and the consumed electric energy, and it is found that the estimated efficiency was higher than 70%. (C) 2010 Elsevier B.V. All rights reserved.