In this study, in order to transform the exit-streams of the solid oxide electrolyzer cells (SOECs) into methane, the nickel-iron supported on ceria-doped gadolinia (GDC) have been tailored to obtain high activity and durability for simultaneous methanation of carbon monoxide and carbon dioxide. The catalysts were prepared by impregnation and characterized by usual analytical techniques. The effects of metals loading and reaction temperature (ranging from 200 to 600 degrees C) on the catalytic activity and selectivity were examined. The catalysts have a total metal loading of 50% wt/wt with respect the support. The high load of metal is due to the foreseen use of the catalyst in the SOECs. The results highlight the superior activity of monometallic Ni/GDC with respect to bimetallic Ni-Fe/GDC catalysts that was ascribed to the paramount role of the GDC support.