The single-phase GdBaCo 2 O 5+x (GBCO) and GBCO–Gd 0.2 Ce 0.8 O 1.9 (GDC) composites (10, 30wt.%) were tested as a cathode material on the anode-supported SOFCs. The cathodes were screen printed on ∼20μm-thick GDC electrolyte that was supported on ∼1mm-thick Ni–GDC anode. The maximum power density (P max ) of 0.56Wcm −2 was obtained for the cells with single-phase GBCO cathode at 600°C under air / 97% H 2 +3% H 2 O gradient. P max decreased to 0.44 and 0.20Wcm −2 when 10wt.% and 30wt.%, respectively, of GDCs were added into GBCO cathodes.