In this study, two-electrode-supported solid oxide cells with the structure of "Ni-Sm doped CeO2 infiltrated porous La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM)vertical bar dense LSGM vertical bar SmBa0.5Sr0.5Co2O5 infiltrated porous LSGM" are fabricated. Fuel cell and steam electrolysis performance at different operating temperature (450-600 degrees C) for different steam content are tested, and reaction mechanism discussed. In the fuel-cell mode, the maximum power density reaches 1.817, 1.345, 0.801 and 0.342 W cm(-2) at 600, 550, 500, and 450 degrees C, respectively. In electrolysis mode, current density at 1.3 V in 70% H2O - 30% H-2 stream is -2.472, -1.616, and -0.727 A cm(-2) at 600, 550, and 500 degrees C, respectively. The durability of the cell is tested for over 351 h. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.