Ceria nanoparticles were added to PBI membranes as free-radical scavengers to minimize the degradation of the polymer bulk. The 7 nm Ceria nanoparticles were synthesized by combustion synthesis and the crystal structure was characterized by X-ray powder diffraction (XRD) and TEM. The oxidative degradation of FBI and PBI-CeO2 membranes was studied under the Fenton test conditions by the weight loss, FTIR and XPS. It was revealed that adding CeO2 as free-radical scavengers greatly improved the chemical stability of the membrane and the degradation occurred at the carbon atom of the benzene ring resulting in the hydrolysis of the C-N/C = N bonds. Besides, ex-situ membrane characterization and in situ durability test revealed that PBI-CeO2-2% membrane exhibited excellent mechanical properties and high proton conductivity of 0.048 S cm(-1) at 150 degrees C and the MEA remained stable during 250 h stability test under a constant current discharge of 200 mA cm(-2). A conclusion is made that PBI membranes blended with a free radical scavenger is a promising approach to enhance the chemical stability for high temperature PEMFC application. (C) 2016 Elsevier B.V. All rights reserved.