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Journal of the Electrochemical Society, Vol.156, No.9, B1022-B1029, 2009
Electrocatalytic Promotion of Palladium Nanoparticles on Hydrogen Oxidation on Ni/GDC Anodes of SOFCs via Spillover
Nanosized palladium particles are introduced to Ni/Gd-doped ceria (Ni/GDC) anodes of solid oxide fuel cells (SOFCs) by wet impregnation using palladium nitrate solution. The electrocatalytic effect of Pd nanoparticles on the oxidation reaction of hydrogen is investigated by electrochemical impedance spectroscopy over the temperature range of 650-900 degrees C. The infiltrated Pd nanoparticles significantly reduce the electrode polarization resistance, and the activation energy for the electrode process associated with low frequencies decreases dramatically with the increase in the loading of Pd nanoparticles, indicating that Pd mainly promotes the adsorption and diffusion processes of the H-2 oxidation reaction on the surface of Ni/GDC anodes. X-ray photoelectron spectroscopy analysis confirms the existence of the Pd/PdOx redox couple during the H-2 oxidation reaction. The significantly enhanced adsorption and diffusion processes of the H-2 oxidation reaction on Pd-impregnated Ni/GDC cermet anodes are most likely due to the significantly promoted hydrogen and oxygen spillover processes over the nanosized Pd/PdO redox couples. The electrode impedance of the oxidation reaction in methane and ethanol fuels is also decreased considerably in the presence of Pd nanoparticles; however, the results show that carbon deposition could not be completely depressed on the Pd-impregnated Ni/GDC anodes under conditions of the present study.
Keywords:adsorption;catalysis;catalysts;cerium compounds;cermets;electrochemical electrodes;electrochemical impedance spectroscopy;gadolinium;nanoparticles;nickel;oxidation;palladium;reduction (chemical);solid oxide fuel cells;surface diffusion