Palladium (Pd) is an attractive cathode catalyst component for solid oxide fuel cells (SOFCs) that has high tendency to agglomerate during operation at around 800 degrees C. This work shows that such agglomeration can be inhibited by alloying Co into Pd. PdO, Pd0.95Co0.05O, Pd0.90Co0.10O, and Pd0.80Co0.20O were synthesized and characterized. Powder X-ray diffraction patterns at 750 and 900 degrees C confirmed that PdO decomposition to Pd which normally occurred at 840 degrees C was suppressed for Co containing Pd alloys while thermal gravimetric analyses indicated improved redox reversibility of PdO <-> Pd conversion for alloys during the thermal cycling between 600 and 900 degrees C. Scanning electron microscopy images supported these arguments. Pd0.90Co0.10+yttria stabilized zirconia (YSZ) electrode (i.e., 10 mol % Co containing PdO-impregnated YSZ electrode) displayed the highest oxygen reduction reaction (ORR) performance and stability. The polarization resistance for ORR on Pd0.90Co0.10+YSZ cathode is only 0.088 Omega cm(2) at 750 degrees C. During polarization test at 750 degrees C, Pd0.90Co0.10+YSZ cathode showed stable performance for 30 h while the performance of Pd+YSZ cathode degraded after 10 h. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.