Sulfur tolerance of Ni/Gd2O3-CeO2 (Ni/GDC) anodes promoted by impregnated palladium nanoparticles is investigated using the electrochemical impedance spectroscopy (EIS) and galvanostatic polarization techniques in the H-2-H2S fuels at 800 degrees C. The anodes are alternately polarized in pure H-2 and H2S-containing H-2 fuels with H2S concentration gradually increased from 5 to 700 ppm at 200 mA cm (2). The degradation in performance for the hydrogen oxidation in H2S-containing H-2 fuels especially at low H2S concentration is substantially smaller on Pd-impregnated Ni/GDC cermet anodes, as compared to that on pure Ni/GDC anodes. The potential of Pd-impregnated Ni/GDC electrodes measured in pure H-2 decreases by 0.07 V after exposure to H2S-containing H-2 fuels, substantially smaller than 0.13 V observed on pure Ni/GDC anodes under identical test conditions. The results show that Pd impregnation significantly enhances the sulfur tolerance of Ni/GDC cermet anodes particularly in the low H2S concentration range (e.g., <100 ppm). The results indicate that the enhanced sulfur tolerance of Pd impregnated Ni/GDC anodes is most likely due to the promotion effect of impregnated Pd nanoparticles on the hydrogen dissociation and diffusion processes. The reduced moderation of the morphology and microstructure of the anodes in the presence of Pd nanoparticles may be the result of weaker interaction or adsorption of sulfur on Ni and GDC phases. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.